When was "fo' sho'" first used in print, television, or music? Or, better yet, when was it standard southern slang?

I can only seem to find Urban Dictionary, et al. references, so I'm turning here for an answer. I know that "fo" ("for") and "sho" ("sure") are common southern dialect replacements, but a debate recently took hold in a social group of mine. When was it "a thing."

Having grown up in south Texas until the year 2000, and having heard people say it my entire youth, I'm fairly confident in it being before then. My friend, on the other hand, is adamant that the expression is dated 2000s and on.

Does anyone know where I might be able to go to get a reasonably reliable answer?

First Uses in Print

The first appearances in print of 'fo sho' that I could find represent a dialectal pronunciation of "for sure". For example, OED provides details for 'sho':

sho | sho', adv.
....
Etymology: Representing a pronunciation of sure....
U.S. (in African-American usage).

I found two, or four appearances of 'fo sho' in 1871, depending on how you count.

"Mighty quah hoss in de pastah?" —
Whah fo' he quah? — "You dunno?
"Kase o' de bah places on him? — "
Dem's whah de woun's wah, fo' sho.

Excerpt from the unattributed poem "Mahs' Lewis's Ride" in the 6 May 1871 issue of Appletons' Journal. Bold emphasis mine.

---

He was ten when Cousin John went dead — 
    Ten fo' sho — "
....
I was nowhah 'longside young Mas' Ran' — 
    Nowhah — no!
  An' I ain't a dwarf fo' sho.
....
"Hole fas', Cesah!" an' wid dat he leap' — 
    Nothin' mo' — 
  Den I loss all else fo' sho.

Excerpts from "Cæsar Rowan" by Thomas Dunn English, in the July 1871 issue of Scribner's Monthly. Bold emphasis mine.

On the surface, the appearances of 'fo sho' in 1871 were "just a cigar". The timing of the appearances, however, midway through the US post-Civil War Reconstruction Era, suggests that the orthographical contortions might have served the more insidious purpose of diminishing a newly empowered social, cultural and political force.

Standard Southern Pronunciation

Writing in the self-published 1893 Some Peculiarities of Speech in Mississippi, Hubert Anthony Shands makes some pertinent observations concerning class differences in the pronunciation of r:

b) R is so seldom pronounced in the middle or at the end of words, by any class of people, that its pronunciation in either of those positions forms an exception. It is quite a peculiar circumstance that a class of very illiterate whites pronounce r much more distinctly than any other people in Mississippi. This pronunciation of r forms, perhaps, the most distinguishing feature of the real "po white trash" dialect as contrasted with the negro dialect. But it is in order to say that no class pronounces r at all uniformly. ... According to Earle, r is frequently dropped from words in the south of England, and especially by the cockneys.

As a matter of speech, in contrast to print, then, Shands suggests that the pronunciation of "for sure" as 'fo sho' was a feature of the Mississippi dialect of English for all classes, with the possible sporadic exception of "po white trash" (illiterate white people).

Shands' observations were of the Mississippi dialect in the late 1800s. The non-rhoticity he observed, wherein r is only pronounced in a prevocalic position, and mentioned as a characteristic of the speech of "any class" became more strongly associated with the dialect of Southern blacks; one vehicle for the strengthening of that association was through the positioning of non-rhoticity in fictional orthographical representations of the putative dialect of Southern blacks. Such circumstances quite possibly precipitated the later and now contemporary thingness of 'fo sho'.

The Slang Thing

As suggested by Erik R. Thomas, in a paper titled "Rural white Southern accents" (2006),

The civil rights struggle seems to have caused both African Americans and Southern whites to stigmatize linguistic variables associated with the other group. It coincides with ... the reversal in which non-rhoticity changed from a prestigious to an unprestigious feature among whites.

The corollary of that reversal of prestigious non-rhoticity for Southern whites was reinforcement of prestigious non-rhoticity for Southern blacks...and, tangentially, supporters of the civil rights movement. That prestige found expression, in the later 1900s and early 2000s, in the gradual and somewhat tentative adoption of a slangish 'fo sho' among both blacks and whites outside of the Southern US, speakers who did not naturally share the dialect wherein non-rhoticity was a continuing affirmation of group identity and, perhaps, an expression of opposition to ongoing social and civil injustices.

Early matches from the Elephind and Library of Congress databases of old newspapers include two dialect poems. From "Mahs' Lewis' Ride," in the Chicago [Illinois] Tribune (May 7, 1871):

"Mighty quah hoss in de pastah?"—

Whah fo' he quah?—"You doano?

"Kase o' de bah places on him?—"

Dem's whah de woun's wah, fo' sho.

From Thomas English, "Cæsar Rowan," in the [Canton, Ohio] Stark County Democrat (July 20, 1871):

Setch a boy as dat when he growed oldah:

Stout an' strong, de maken' of a man;

Dis yeh chin jes' retched up to his shouldah:

I was nowhah 'longside young Mas' Ran'—

An' I ain't a dwarf fo' sho.

As user9825893y50932 notes in a comment beneath the posted question, a Google Books search yields a number of unique matches—four—from the period 1871–1891. The 1871 match is from Scribner's Monthly (July 1871) and consists of a longer version of "Cæsar Rowan," quoted in the Stark County Democrat item noted above. Other relevant matches from that same search include this one from James Maitland, "Wedded in Death," in Belgravia (July 1874):

'I bring um letter fo' massa,' replied the negro. 'I knock two, tree, five time at de door. No come answer. Fo' sho', I tink, massa gone dead. Den I knock um loud fo' rouse him.'

From M. Sheffey Peters, "Juba's Coon-Hunt," in Peterson's Magazine (March 1884):

But almost in the instant of speaking, he and his two companions darted forward, lured once again by the persistent baying of the hound.

"He's in dead earnes' dis time, fo' sho'," said Billy. "Dat's de genewine coon-yelp."

And from Wenona Gilman, Saddle & Sentiment, serialized in Outing (October 1891 and March 1892), which uses the phrase four times:

" Dar he is, suh!" exclaimed Watt, with a comprehensive wave of the hand. "He ain't no beauty fo' sho', 'specially dat head, but den he don' run wid his head. Look at dem quarters ! See how well he is ribbed back! See dem hocks! no place for a curb dar. See how flat an' hard dem legs looks, an' sich a shoulder! Umph-umpy! I tell you, Mars John, dar's speed in him, and he's sho' t' be game frum his breedin'!"

...

"Dat seem so, Mars John, but taint, fo' sho'!" he replied, shaking his head slowly.

...

["]Der ain't no better breed 'n' dat agoin'. you heah Watt! Mars John thinks he know a heap about hosses, an' he do, sah, he do fo' sho', but Watt ain't been brung up among thoroughbreds sense he wus knee high to a duck fur nuthin'."

...

["]I done clar' fo' goodness I'se got de creeps all ober me. Pears to me dat she's been a pinin' away jis' fur a look at de ole place. It do fo' sho'."

Instances of "fo' sho'" are fairly common in dialect fiction at the turn of the twentieth century. For example, from George Cable, John March: Southerner (1894):

Johanna, with three leaping strides, was out of the water, across the fence, and scampering over ledges and loose stones toward the house, mad with the joy of her news:

"Mahse John Wesley! Mahse John Wesley!"—up the front steps, into the great porch and through the hall—"Mahse John Wesley! Mahse John Wesley! De waugh done done! De waugh ove' dis time fo' sho'! Glory! Glory!"—down the back steps, into the kitchen—"Mahse John Wesley!"—out again and off to the stables—"Mahse John Wesley!"

From Elizabeth Robins, The Open Question: A Tale of Two Temperaments (1898) [combined snippets]:

Venus seemed to think it incumbent upon her to hold up her end of the conversation.

"Huh! Can't say fo' sho' why I'm carryin' on like dis yere." She mopped her eyes. "Miss Val gone away laffin' fit to kill."

From Marion Haskell, "Toteheap," in Harper's Magazine (May 1901):

"Mahstah," he answered, turning to face me, "what mek you ax me dat? Whey I got dis mule? I stole um, an' dat's whey I got um, fo' sho'. I 'ain' nebbah tuk anuddah Gawd's t'ing f'om nobody. I wuk while I kin wuk, sez I, an' when I can' wuk no mo', and I 'ain't got no white folks, den I gwine do like de 'possum een de wintah-time—I jes gwine to sit dyah an' suck my paws. Yessah! But I tuk dat mule. It come about dis way: ...

And from Rosa Lee, "Unc' Handy's Witch," in The Southern Workman (1905):

"Hurrah!" cried Harry. "Oh, Aunt Kitty, is it going to keep up? Will we have a snowy Christmas? How deep will it be?" "And oh! can we make a snow man and a tar baby?" put in Betty, climbing to her nurse's knee, as Harry flung himself on the rug at her feet.

"Law yes, honey. Y'all kin jes 'pend on it, hit's 'gwine snow fo' sho' dis time; 'tain' no nonsense in dem clouds ober yondah, dey done look jes' lak' dat de time er de big blizzard."

One very famous work that contains the expression "fo' sho'" is Eugene O'Neill, The Emperor Jones (1920):

JONES {scornfully}. Dat fool no-count nigger! Does you think I'se scared o' him? I stands him on his thick head more'n once befo' dis, and I does it again if he come in my way— {fiercely}. And dis time I leave him a dead nigger fo' sho'!

It is difficult to confidently estimate how old the pronunciation "fo' sho'" for "for sure" is, but the written form "fo' sho'" goes back at least as far as the first decade after the U.S. Civil War. The more recent popularity of "fo' sho'" is almost certainly an extension of the earlier dialectal pronunciation.

The earliest reference I can find to this phrase is from a hip-hop album recorded in 1993 (released 1994), On Anotha Level by Anotha Level. The song is titled "Fo Sho Shot."