The colloquial phrase you’re so sharp you’ll cut yourself is used as an observation, a reproof or a warning implying over-cleverness.
This phrase plays on two meanings of the adjective sharp:
– literal meaning: cutting;
– figurative meaning: keen-witted.
—Cf. also the phrase the sharpest —— in the ——.
The phrase you’re so sharp you’ll cut yourself occurs, for example, in the column Odd Man Out, by Martyn Harris, published in The Daily Telegraph (London, England) of Saturday 21st December 1991:
The diary of Sarah aged 10¼
DO YOU two want to go to the pantomime, Dad says, so Tom does his Herman Munster moan, and I say, oh God, you’re going to put us in another article in your newspaper aren’t you? And my teacher’s going to read it out in class and I’m going to just die in front of Julie and Rachel. Why can’t you just hire some kids or something?
So on Thursday we go down the West End in a proper black taxi, which Dad usually says are Far Too Dear and what’s wrong with your legs? But he says it’s all right this time because it goes on expenses, and I say that I thought taxis went on petrol. And Dad says you’re getting that sharp you’ll cut yourself one of these days, and I say that’s a cliché, Dad, and he says OK, Dorothy Parker, you write the rotten article.
The earliest occurrences of the phrase you’re so sharp you’ll cut yourself and variants that I have found are as follows, in chronological order:
1-: From the account of a public meeting of ratepayers, held at Tyldesley, “to consider the propriety of again requesting the Local Board to abandon the Cutacre Water Scheme”—account published in the Leigh Chronicle. Weekly District Advertiser for Astley, Atherton, Bedford, Lowton and Tyldesley (Leigh, Lancashire, England) of Saturday 17th March 1866:
Mr. James Hope: Mr. Chairman and Gentlemen,—I beg to move “That this meeting is fully convinced that the carrying out of the Cutacre water scheme will be attended with great risk, and under the most favourable circumstances would entail upon the township ruinous and needless expense, which the Board would not be justified in incurring in direct opposition to the wishes of the ratepayers, who believe that one individual alone can be pecuniarily benefitted thereby.” Those who are of that opinion will please say so by a show of hands. (Loud laughter, and a voice: You are getting on too sharp, you’ll cut yourself, you are taking the chairman’s position.)
2-: From the account of a public meeting held by the Rev. W. H. Tunnicliffe, who was one of the two persons that had been selected to fill a vacancy on the Soothill School Board—account published in The Batley Reporter, and Guardian (Batley, Yorkshire, England) of Saturday 8th June 1872:
The Working Man: I say this is a working man’s question. (Disorder.)
Mr. Tunnicliffe: You said just a moment ago you wanted to criticise my remarks, and now you say it is a working man’s question. (Disorder.)
A Voice: Let the man speak; he has as much right to speak as any of you. (Disorder.)
The Working Man (to Mr. Tunnicliffe): Don’t you be so sharp, or you may cut yourself. (Hear, hear.)
Mr. Tunnicliffe asked the man to look sharp, as he (the speaker) wanted to be going.
The disorder now became so great that the working man sat down.
3-: From the account of the revision of the parliamentary and municipal voting lists for the borough of Sheffield, held at the Town Hall, published in The Sheffield & Rotherham Independent (Sheffield, Yorkshire, England) of Thursday 30th September 1880—Mr. Clegg represented the Liberals:
Mr. Clegg objected to a lodger claim by John George Robinson, 7, Mandeville street, Darnall.—Mr. Robinson said he occupied a bed room in his father’s house.—Mr. Clegg: Have you the general run of the house?—Mr. Robinson: What do you mean?—Do you live in the house? Live! I don’t die in it.—Mr. Clegg: Don’t be too sharp, or you’ll cut yourself. Do you have the run of the house?—Mr. Robinson: I don’t know what you mean.—Mr. Clegg: Do you say, “Please, father, may I go into the kitchen?” (Laughter.) Mr. Robinson: That is too personal.—Claim disallowed.
4-: From Chapter 27 of The Black Shaft; Or, The Miner’s Daughter—A Mystery, by the Irish engineer, author and translator Henry Frith (1840-1917), published in the Alnwick and County Gazette (Alnwick, Northumberland, England) of Saturday 25th April 1885:
“I’ve found that hammer! There!”
“What good can the hammer do you?”
“Can’t it? Suppose a man finds a hammer which another man, a gentleman, has hid for some reason—a good reason no doubt.”
“Well? You are too sharp, Harry; you will cut yourself some day.”
“Shall I? You’ll see, Sarah. Well, I says nothin’. But when I find a hammer which a gentleman has had, and the hammer is all over blood!”
5-: From The Helensburgh News (Helensburgh, Dunbartonshire, Scotland) of Thursday 24th September 1885:
NOTES BY OUR RAMBLING REPORTER.
Look here! You know we can’t pass the silly season without our own little particular sea serpent story, so here it is—
Scene: The Office of the Helensburgh News—The Deputy Sub-Editor discovered musing. Three slaughtered poets await their coffins. Slow music. The door opens, and enters mysterious stranger. He is long and lank and lean, his hat is ventilated on old and unimproved principles; his boots, too, admit airy freedom; his coat has the recommendation of extreme antiquity; and his nose flames like a meteor in the night.
Mysterious Stranger—Say, guv’nor, is the editor in?
Dep. Sub-Ed—No, he aint sic].
M.S.—Will he be in soon?
D.S.E.—No, he won’t.
M.S.—Can I wait?
D.S.E.—No, you can’t.
M.S.—If I called again, would I see him?
D.S.E.—No, you wouldn’t. He has gone for a short holiday, tiger hunting in the Madras Presidency. I’ll tell him you called; he’ll be sorry to have missed you.
M.S.—Have you at heart the best interests of your newspaper?
D.S.E.—Is it the big gooseberry or the gigantic cabbage?
M.S.—No, sir. You have before you the man who has seen before him the sea-serpent—the sea-serpent, sir. My glass brought it as near to me as you are. Will I write it up? Will I electrify your readers? Will I place the Helensburgh News on the pinnacle of art and science. Seven-and-six are my terms.
D.S.E.—Look here, stranger. I can’t do it. When we want the sea-serpent interviewed, we turn on one of our own staff to do the job. We send him down to the Esplanade, furnished with a powerful glass.
M.S.—I suspect, young man, that our telescopes were made by the same firm.
D.S.E.—Telescope, you idiot! Our patent magnifying glass is a glass of whisky.
M.S.—Look here, young man. Your wit’s too sharp. You’ll cut yourself some day, and be carried home to your sorrowing relatives.
Exit. Slow music. Curtain.
6-: From Payment, by the British journalist and author Barry Pain (1864-1928), published in The Galveston Daily News (Galveston, Texas, USA) of Sunday 6th January 1895:
The assistant attached the labels to the bottles hurriedly.
“There you are,” he said as he gave them to the errand boy. “Mrs. Wilkins, No. 13, The Crescent.”
“Thirlby’s the nime you’ve put on the piper.”
“Oh, is it?” said the assistant. “Indeed, shouldn’t wonder. Don’t you be too sharp, or you may cut yourself. Mrs. Wilkins lets apartments and the Thirlbys live there. Now, if you’re quite satisfied perhaps you’ll run along.”
The errand boy grinned sheepishly and went off with the bottles.