How can I explain to people that the phrase “off of ” is grammatically incorrect? [closed]

How can I explain to people that the phrase off of is grammatically incorrect?

I‘ve heard this phrase used a lot, especially by Americans (though they aren't the only ones).

In my understanding, off of should usually be replaced by off, as in,

I took the book off the shelf

as opposed to

I took the book off of the shelf

Am I wrong? Or is there perhaps some simple way I can explain this to most people?

I don't know how you can explain to people in general that it's grammatically incorrect, but here is one idea: when you go to a James Brown tribute concert and the singer says "Get up offa that thing" what you could do is to trounce the security guards, climb on to the stage, pounce onto the singer, grab the microphone and say "In fact you should be saying not 'get up offa that thing' but 'get up off that thing' since 'offa' is grammatically incorrect." I'm sure everyone will thank you for your grammatical corrections.

Being serious for a moment though, it's very difficult to decide what is or is not "grammatically correct". E.g. in the UK we say "outside my house" but US people often say "outside of my house". How can you actually decide which of these two is grammatically correct? Unfortunately it's not possible since English grammar is not a science like physics but merely a description of what people actually do, and that has changed very significantly over the years. If I was teaching someone English I would definitely say "off" is correct and "off of" is wrong, but this kind of decision is based on intuition, based on the usages of educated native speakers.

How can I explain to people that the phrase "off of" is grammatically incorrect?

You can't, because it's not.

There are thousands of examples of “off of” in the Corpus of Contemporary American English, not just in spoken English, but in magazines, newspapers, and academic journals as well. “Off of” is well-established as standard in American English. Plain “off” may be stylistically preferable in many cases, but it is simply not a rule of English grammar that if a word could be removed it must be removed. Some people seem to think that such a rule exists. It does not.

The phrase "off of" has a long history, which, according to the OED, stretches back roughly 500 years. If you want to consider it to be "wrong", then it certainly has a lot of staying power. Here are their quotations using "off of":

?c1450 in G. Müller Aus mittelengl. Medizintexten (1929) 116 Take a sponfull of e licour..of of e fyir and sette it in good place tyl at it be ny colde, soo as ou mayst suffryn to holdyn er-in in hand.
a1616 SHAKESPEARE Henry VI, Pt. 2 (1623) II. i. 98 A fall off of [1594 Falling off on] a Tree.
1667 A. MARVELL Corr. in Wks. (1875) II. 224 The Lords and we cannot yet get off of the difficultyes risen betwixt us.
1678 J. BUNYAN Pilgrim's Progress 49 About a furlong off of the Porters Lodge.
1712 R. STEELE Spectator No. 306. 6, I could not keep my Eyes off of her.
1720 D. DEFOE Mem. Cavalier 281, I had perswaded him off of that.
1748 S. RICHARDSON Clarissa V. xiii. 132 Biting my lip, [was to indicate] Get off of that, as fast as possible.
1775 P. OLIVER in T. Hutchinson's Diary 7 Dec. I. 581 A Rebell Pirate..taken..off of Cape Ann.
a1805 in F. J. Child Eng. & Sc. Pop. Ballads (1894) V. IX. 106/2 Aff o the weather [read wether] he took the skin, An rowt his bonny lady in.
1824 J. WIGHT Mornings at Bow St. 21 Two young men..were charged by a watchman with having ‘bother'd him on his bate,’ and refused to ‘go along off of it when he tould 'em.’
1843 T. C. HALIBURTON Attaché 1st Ser. II. xii. 210 The groom has stole her oats, forgot to give her water, and let her make a supper sometimes off of her nasty, mouldy, filthy beddin'.
1868 HARTLEY Clock Alm. in Leeds Mercury Weekly Suppl. (1895) 5 Oct., He connot forshame To lift up his een off o' th' graand.
1875 P. BROOKS New Starts in Life viii. 129 If you could have filled his pockets with gold, and feasted his hunger off of silver dishes.
1884 ‘M. TWAIN’ Adventures Huckleberry Finn vi. 45 I'd borrow two or three dollars off of the judge for him.
1909 G. GREIG Mains's Wooin' 6 He's swallowed the dictionar', min, an's tryin' to get 'er aff o's stammack.
a1922 T. S. ELIOT Waste Land Drafts (1971) 5 The reputation the place gets, off of a few barflies.
1962 F. NORMAN Guntz i. 15, I got hold of this very very old typewriter off of a friend of mine.
1974 J. STUBBS Painted Face xxiii. 284 Get off of me, will you, sir?
1990 B. ROCHE Poor Beast in Rain II. i. 44, I was hangin' around here all the time, gettin' sweet nothin' off of you.

This may perhaps be more common in American English nowadays, but it certainly didn't originate there.