Green’s Dictionary of Slang

knife v.

(US) to attack, either verbally or in print, in an underhand manner; thus knifing n.

1888		Nation 10 May 375/1: The strongest men in the party cannot be nominated, because they are hateful to the Blaine faction, and are certain to be knifed in the Convention in case Blaine does not get the nomination [DA].
1911		H.S. Harrison Queed 323: What chance’d there be of namin’ to lead the party in the city the man who had knifed the party in the State?
1920		Ade Hand-made Fables 74: Did he become embittered and rave about being Knifed by those whom he had pulled out of the Ditch?
1932		J.T. Farrell ‘A Practical Joke’ in Short Stories (1937) 187: I’d like to see you fellows take such a knifing.
1935		(con. 1920s) J.T. Farrell Judgement Day in Studs Lonigan (1936) 527: He would have been state’s attorney years ago if the newspapers hadn’t knifed him.
1940		G. Marx letter 16 Dec. in Groucho Letters (1967) 151: The critics ought to be ashamed of themselves for the knifing they gave it.
1952		W. Winchell On Broadway 5 Sept. [synd. col.] Robert Wagner, Jr., still sizzling over the ‘knifing’ he got from Democrats.
1953		J. Thompson Criminal (1993) 11: Others that had tried to knife me every time I turned my back.
1978		L. Kramer Faggots 170: Dinky knife you?

SE in slang uses

In phrases

knife up (v.)

(Aus.) to share.

1983

R. Aven-Bray Ridgey-Didge Oz Jack Lang 33: Knife Up Share.

In exclamations

knife it! [i.e. cut it short]

stop!, don’t go on!

1812		Vaux Vocab. of the Flash Lang.
1835		G. Kent Modern Flash Dict.
1846		Swell’s Night Guide 123/2: Knife it, stow it, be quiet.
1859, 1860		Hotten Dict. of Modern Sl. etc.
1873		Sl. Dict.
1895		C. Crowe Aus. Sl. Dict. 42: Knife It, stop the conversation.