Is "whom's" a valid contraction?

Solution 1:

There is no official list of valid contractions for the English language.

We might be able to logically deduce that whom’s is “invalid” if there were some general syntactic issue with contracting the auxiliaries is or has in this grammatical context (after a wh-fronted object pronoun in a sentence with inversion). But there isn't; Whom's is analogous to the very normal use of What's in the following contexts:

• “What’s he done?” (for “What has he done?”)
• "What’s he doing?" (for “What is he doing?”)

So there is no definite answer to your question.

Note that whom itself is considered by some linguists to be on its last legs ("almost an ex-word", Geoff Pullum, "The Coming Death of whom", cited by John Lawler in a post on this site; see also the collection of links in the post "It's a made-up word used to trick students", Benjamin Zimmer, both on Language Log). Asking about the validity of the contraction whom's without taking the dubious status of whom into account might be almost like asking about the validity of the contraction thou'rt without considering the obsolescence of thou. In other words, the rarity of whom's might be nothing more than an effect of the ill health of whom.

Regardless of whether it is "valid", whom's has seen some tiny amount of contemporary use:

• Whom's he calling a coward? Antifa or the do-nothing Police?

  • Knight1_of_Sunset, 2020/11/15, The Donald forum

• Going to the intermediate, he wants a new place, but whom's he gonna take it from?

  • Jyrel, 2019/7/30, posted in thread "Huntik: Venture into the unknown (OOC)", Sufficient Velocity forum

• So in a few years when he needs a website whom’s he going to call?

  • Nanci, at 23:11 , "Sales Funnels For Prospects— Got One?", June 3, 2017 by SLASH PODCAST

• Where is he now?
  Whom's he kissing?

  • I miss him badly, my soul aches, Екатерина Передереева

All of the examples of Whom's he... that I could find on the internet stood for Whom is he..., not for Whom has he....

For older examples, see Sven Yargs's excellent answer.

Solution 2:

Although in recent years "whom's" seems to appear in print most frequently as an ill-advised possessive (in place of "whose"), in the past it appeared fairly often as a contraction—usually, but not always, of "whom is."

An examination of Google Books search results in which "whom's" functions as a contraction suggests that these matches fall into three primary categories: instances in various settings, from approximately 1606 to 1754; instances in poetry and metrical dramatic verse from 1848 to 1915; and instances in dialogue from 1877 to 1922. Here are some examples of instances from each of these three categories.

Seventeenth- and eighteenth-century instances

From Samuel Rowlands, "A Terrible Battell Betweene the Two Consumers of the Whole World: Time and Death" (1606[?]), in The Complete Works of Samuel Rowlands, 1598-1628 (1880):

And then I go to baile an honest man, / Lies in the Counter for a little debt, / Whom's creditor in most extreames he can / Doth deale withal, now he is in the net; / He sweares heele keepe him there this dozen yeare, / Yet the knaue lies, this night ile set him clear

This instance is unusual in that "whom's" may be a contraction not of whom and a following verb (is or has) but of whom and a following possessive (his).

From John Davies, "Summa Totalis, Or All in All, and the Same for Euer" (1607), reprinted in The Complete Works of John Davies of Hereford (15..-1618) (1878):

Hee's Glories Sunne, whose Shade is constant sight; / Then can no Shade of change eclipse his Blisse, / In whom's no darknes ; for, he blinds the sight / Of bright-Ey'd Angels, with his glory bright.

From Francis Beaumont & John Fletcher, Cupid's Revenge (by 1613):

Nisus. Is not this a fine marriage?

Agenor. Yes, yes ; let it alone.

Dorialus. Ay, ay, the king may marry whom's list. Let's talk of other matters.

A footnote appended to an 1843 edition of the play reports, "whom's list} Altered by the modern editors to 'whom he list.'" But if the original term is indeed a contraction, it presumably amounts to a telescoping of "whomever he is," with "list" bearing a meaning akin to "inclined."

From Henry More, "The Argument of Psychathanasia, Or The Immortality of the Soul" (1647), in The Complete Poems of Dr. Henry More (1614-1687) (1878):

O You stiff-standers for ag'd Ptolemee, / I heartily praise your humble reverence / If willingly given to Antiquitie; / But when of him in whom's your confidence, / Or your own reason and experience / In those same arts, you find those things are true / That utterly oppugne our outward sense, / Then are you forc'd to sense to bid adieu, / Not what your sense gainsayes to holden straight untrue.

From "John Harrington to His Sister, on Flostella's Death, 1647," in Nugæ Antiquæ: Being a Miscellaneous Collection of Original Papers in Prose and Verse; Written in the Reigns of Henry VIII, Queen Mary, King James, &c., volume 2 (1779):

Is any shepherd's ear so deaf to fame, so used to tender bleatings,—that has not heard of fair Flostella's death! Or any nymph to whom hath not arriv'd that funeral knell which groan'd this fair to earth and made all hearts congeal? If such—thrice happy ye! to whom's as yet unfelt distress'd Arcadia's loss, whose best beloved fair cloysters in the dust. Died she alone? No, gentle sister! Hundreds did seem to die in sorrow with her.

And from Robert Howard, The Vestal Virgin, Or, The Roman Ladies: A Tragedy (by 1665):

Artabaces. Now idle fortune, modestly stand by, / And let just Love dispose of Victory.

{They fight, Mutius falls, and Sulpitius stands staggering.}

Tiridates. Now, Sulpitius, to whom's Hersilia due?

From "An Acrostick," a poem by Anthony Wood, composed in December 1669, in The Life and Times of Anthony Wood: Antiquary, of Oxford, 1632–1695, Described by Himself, volume 2 (1892):

Fancie's desire! where wit enthronned lyes / Ordaind Mecaenas-like of matchles parts / With whom's the fountaine of most learned arts / Lo! in whose lyons brest remains maintaind / In royall state a loyall heart unstaind.

From John Bunyan, "The General Epistle of James," in Scriptural Poems (1701):

But every man is tempted when he's drawn / Away, and by his lusts prevail'd upon; / Then when lust hath conceiv'd, it ushereth / In sin, and sin when finished brings death. / Err not, my brethren, whom I dearly love, / Each good and perfect gift is from above, / Down from th' original of lights descending, / With whom's no change, nor shadow thereto tending, / According to his own good pleasure, he / Begat us with the word of truth, that we / Should as the first fruits of his creatures be.

From A Collection of Hymns of the Children of God in All Ages (1754):

These are they, on whom's bestow'd / The name Saints, and holy, / The seal'd Servants of our God, / First-fruits from Earth truly.

Appearances in nineteenth- and early-twentieth-century poetry

From Henry Sutton, "Extracts from 'Zadock'" in Poems (1848):

For there's not one, to whom's not given / Some little lineament of Heaven, / Some symbol, at the least, and sign / Of what should be, if it is not within,— / Reminding of the death of sin / The Life of the Divine!

From John Lee, The Emigrant: A Lyric Poem, volume 1 (1853):

Then they to Jesus' joy shall have access, / And still Jehovah glorify and bless; / None, Demas-like, whom lucre did defile, / But Israelites indeed, in whom's no guile.

Although Lee's grasp of meter is rather weak and intermittent, metrical considerations seem to be responsible for his choice of "whom's" here; in any event, the usage is certainly grammatical.

From "Some New Year's Gifts," in Fun (January 10, 1863):

To TENNYSON, on whom's bestowed / The laureateship—he ought to sing— / I'd give a subject for an ode, / To throneless Greece I'd give a king.

From J. Mackey, "My Lovely Carri," in The Volunteer Rifle Corp Songster (1860):

Poets may portray to the mind / The charms of Hebe, or of Laura; / They'll not find one in whom's combined / Such charms as hath my lovely Carri.

From "The Victim of Hymen" in Once a Week (March 6, 1869):

"Look now! Whom's he meeting?—maid, lady, and baby, / It must be his wife, by the way that she smiled; / He's stopping again—why, what can the delay be?— / Good gracious, Dalrymple, he's kissing his child!

From an 1884 translation of the Fables of La Fontaine:

'Tis right our generosity to show, / But unto whom's the needful point to know. / As to ungrateful men, their doom stands fast, / They die a miserable death at last.

From a poem fragment embedded in F.C. Philips, One Never Knows, volume 2 (1893):

Some lines he had once read came back to him:

"Good night—good sleep—good rest from sorrow / To those for whom's no good to-morrow. / Ye gods be gentle to all these!"

From "CIX. [Mountaineering]," in Thomas Sinton, The Poetry of Badenoch (1906):

And when it draws towards evening and the gallants make their round—Munro and Mackenzie, the sulky men in whom's no ruth,—needs I away must run from that abode with speed, and I'll betake me to the upper part of the jutting hills, and no fear to me from the north.

From T.E. Ellis, Lanval: A Drama in Four Acts* (1908):

LYNETTE. No, but 'tis horrible / To see a gallant and sweet-favoured man / Lie at the feet of a grim follower / Of power and war; a priest of policy, / A sour disciple of the arts of state / In whom's no pleasure, gaiety or wit, / But sullen strength.

From L. Adda Nichols Bigelow, "Delphine," in From Sea to Sea: Complete Poems (1915):

To him that overcometh , I / With hidden manna will supply; / To him that hath an ear to hear / The Spirit ever speaketh clear; / And they that understand shall own / A new name written in white stone, / Which no man knoweth saving he / To whom's revealed the mystery; / The simple token of a friend / That one the other doth commend.

And from a 1915 translation of Hugo von Hofmannsthal, Venice Preserved: A Tragedy in Five Acts:

Pierre.— Yes, Renault! Yes, Capello! / Into your faces,—the earmarks of a coward! / Or one who likes to fish in troubled waters!— / While other men—

Renault.— For whom's this meant?

Pierre.— For you! / You common tradesman, dealer in gold and slaves, / Who thought to make rich money with our blood!

Late nineteenth- and early twentieth-century instances from dialogue

From "Tim Kenney: A Story of Irish Life," in The Shamrock (August 4, 1877):

"Well, Mr. Mooney, it's the way of the world—if I may so express it—the juvenile mimbers as they get up coalesce an' get homes o' their own, as the poet would say. You were once a sthrappin' bould boy yourself, Mat, I've heerd the ould people, many of whom's now no more, say."

"Och, the world's changed, John, since thin."

This instance is rendered in Irish dialect and features "whom's" in a setting where "whom're" would seem to be a more syntactically defensible choice. Nevertheless, it stands as the earliest in an extensive series of matches for "whom's" in nineteenth and early twentieth-centiry dialogue.

From Mary Sleight, Prairie Days, Or, Our Home in the Far West (1879):

"Whom's it for?" asked Dick, as Maud came running toward them, waving the note over her head.

"For all of you, I think," said Maud, reading aloud the address.

This instance is far more typical of the category than the slightly earlier instance from The Shamrock—specifically because it involve use of "whom's" linked to a preposition that comes at the end of the phrase in which it appears. This is in sharp contrast to the poetic instances that appear in the previous category, which tend to park the preposition in front of "whom's."

From a review (with excerpts) of Victor Hugo, Torquemada, in The Western Galaxy (May 1888):

Sancho. {Eyes lifted to heaven.} There's something soft and good pervades all space. {Plucks flowers for his bouquet while Rosa runs after butterflies. He gazes after her.} Rosa!

Rosa. {Turns back, looking at the flowers in Sancho's hand.} For whom's this nosegay?

Sancho. Guess.

From Ian Maclaren, "Afterwards," in McClure's Magazine (April 1895):

"A telegram." It was the shattering of a dream. "How wicked of some horrid person! Business ought not be allowed to enter paradise. Let's hope it's pleasure; perhaps some one has won a lot of money at Monte Carlo, and wishes us to celebrate the affair."

"Whom's it for? Oh! Mr. Edward Trevor; then it's a brief by telegraph, I suppose. Some millionaire's will case, and the Attorney-General can't manage it alone. What a man he is, to have briefs in holiday time.

From Marian Phillips, "At the Point of a Spear," in The Illustrated American (April 13, 1896):

"Sit down and out with it, Bart," said Lawrence by way of welcome. "Dinner won't be ready for half an hour." Barton let down his muscular lenght on an old steamer-chair near his friend and glanced at the letter in Lawrence's hand.

"Whom's that from?" he began in a rumbling bass, for which the girls had christened him the "Bassoon."

From George Turner, The Taskmasters (1902):

"O, that's all right," Mayhew answered awkwardly. "Where shall I meet him?"

"At Starkwater."

At Starkwater; whom's he stopping with there?"

"Nobody; he's in the old mill—the lower one—sleeping just for a few days, keeping out of sight."

From Henry Hartland, The Royal End: A Romance (1909):

"I give you up," said Ponty. "You're in one of your mystifying moods, and your long-suffering friends must wait until it passes." Then nodding towards the open letter in her lap, "Whom's your letter from?" he asked

...

"What will you give me," Ponty asked, when he had opened and glanced at it [a newly arrived telegram], "if I'll read this out?"

"Whom's it from?" asked Lucilla.

Again, the grammaticality of "whom's" isn't in question—certainly not in the way that Ponty's question "What will you give me if I'll read this out?" is—but the combination of the formal "whom" with the informal preposition-ending sentence structure strikes an odd tonal chord.

From Leonard Merrick, "The Reconciliation," in The Man Who Understood Women: and Other Stories, second edition (1911/1919):

"Emerson— Have you read Emerson?"

"Whom's it by?" I asked viciously. I saw her shudder.

From a 1913 translation of Hermann Sudermann, The Song of Songs:

Then it seemed to them they heard the trot of horses starting in the courtyard and dying away on the other side of the gates.

Whom's he gone to fetch?" asked Walter. "We're not ready for seconds yet."

Here, the contraction "whom's" stands for "whom has."

Likewise, in Mrs. John Lane, Maria Again, (1915):

"Could and would—till you're found out! Offering me in July a Chinese duck, frozen stiff, and calling it Aylesbury!" And Maria pointed an accusing forefinger at a forlorn bird reposing on a fish mortuary-slab.

"In whom's one to put one's trust?" and she stabbed the erring tradesman with a stare like an icicle.

From a translation by Carl Roberts of Nicholas Evreinov "A Merry Death, A Harlequinade," in Five Russian Plays: With One from the Ukrainian (1916):

HARLEQUIN: We must lay [the table] for three.

PIERROT: Three?

HARLEQUIN: Yes.

Whom's the the third for?

HARLEQUIN: For Death.

...

HARLEQUIN: Come, come! I was joking. Death will sup on me. That's sufficient for her. But, all the same, lay for three. (Lights the lamp.)

PIERROT: But whom's the third for?

The usage here seems to me to be less smooth. Perhaps this is because Pierrot adopts the informal (by 1916 literary standards) practice of ending his sentences with a preposition and yet at the same time maintains the formal distinction between whom and who, even as he compresses "whom is" into a contraction. The contradictions in register produce a strange and faintly ludicrous effect, which may be the author's (or translator's) intention.

From Ragna Eskil, Lottie Sees It Through (1918):

RUTH (tactfully coming to the rescue). You haven't read your letter, Lottie.

PRISCILLA (glad of a pretext to change the subject). Whom's it from?

From Clara Laughlin, The Keys of Heaven (1918):

"I know how you feel about it, Gov'nor," Dan began boldly. "I knew it before I told you. And I want you to kno that I don't resent it. From your point of view, it's true. But from mine, it ain't. Knockin' around minin' camps like I've done, I've seen a lot; and I figure out that men are of three sort, as far as women are concerned. There's those that almost any woman can satisfy for a little while, and prob'ly no woman could hold—just human animals, they are; not so decent as most of the savages I've known. Then, even on the edges of things like where I've lived, I've met men like you who've got an ideal, a dream, and are holdin' out for it. But the majority are in my class, I think: the world's full of women one of whom's likely to content us as much as any other would; we don't expect perfection; we just get in the notion of marryin'—havin' a home and a wife and kids—and when we're feelin' that way—! ..."

This instance is notable because here the speaker doesn't dangle the preposition at the end of the sentence, but rather tucks it in front of "whom's" in the approved 1900s grammar-school way.

From Arthur Johnson, "A Flight From the Fireside," in Harper's Magazine (February 1919):

"How about a Revue? You always promised, Pete, to take me to a midnight Revue!"

"Sorry. We'll have to be going presently."

"Oh, is Molly here? Whom's she with?"

From Gilda Varesi & Dolly Byrne, "Enter Madame," in Hearst's Magazine (November 1920):

John (resentfully)—I'm glad Aline came along. She might as well know what of a crazy family she's marrying into.

Gerald (shortly)—Whom's she marrying?

John (proudly)—Me.

From Alfred Coppard, "Cotton," in Adam & Eve & Pinch Me: Tales (1922):

"Ah, and they say Parson Rudwent won't last out the night."

"And whom's to bury us then?" asked Ann.

This is the only instance I came across from this category of usage in which "whom's" would more properly be "who's"—that is, in which the choice of whom over who is technically unjustified.

And from Edward Benson, Peter (1922):

The serpent aspect showed its innocuous fangs. "Monster," she said to Peter. "Sit down and tell me at once what's going on next door. Whom's my Christopher flirting with?"

"Everybody," said Peter. "He sent me away to flirt with you. Let's begin. Shall I begin? Tell me why you and he should always remain young when all the rest of us are as old as the hills."

Conclusions

Most of the seventeenth- and eighteenth-century instances of "whom's" as a contraction seem to have used the form for metrical reasons—and virtually all of the poetical instances from 1848 to 1915 seem to have reflect this motive.

The category of instances that I find most intriguing is the one involving dialogue from 1877 to 1915, In these cases the use of "whom's" seems to be reflecting contemporaneous spoken English—at least in the social strata to which the speakers belong. That the usage qualified as standard English at the time is by no means clear, however.

The contraction "whom's" has become much rarer in published writing since the 1920s, but during its heyday it appears repeatedly in contexts where the point doesn't seem to have been to make the speaker look bad—often enough to indicate to me that a significant number of people at that time really did use it conversationally in that way.

As I noted earlier, one feature of this usage in dialogue is that it typically involved use of a dangling prepositon—"whom's it from?" "whom's it for?" "whom's it by?" "whom's he stopping with?" Moreover, the contraction "whom's" usually appeared in interrogative constructions.

I don't know why this usage fell out of favor after the 1920s, but it is certainly not at all common today.