Green’s Dictionary of Slang

stop it! be quiet! shut up!

1890		‘Rolf Boldrewood’ Colonial Reformer II 62: ‘All right, old boy, knock it off,’ exclaimed Parklands.
1906		E. Dyson Fact’ry ’Ands 28: Knock it off, George Henry [...] Knock it off, there’s er good feller.
1927		(con. 1918) J.W. Thomason Red Pants 90: Aw – knock it off!
1952		‘Hal Ellson’ Golden Spike 152: Now I say knock it off!
1963		M. Spillane Return of the Hood 55: Knock it off, Shaffer. Are you coming through?
1977		E. Bunker Animal Factory 145: ‘Knock it off!’ the lieutenant said.
1987		T. Wolfe Bonfire of the Vanities 215: Knock it off. I can’t hear myself talk.
1997		C. Hiaasen Lucky You 231: Knock that shit off!
2002		J. Ridley Conversation with the Mann 36: What it translated to was: ‘Knock it off, niggers’.
2012		T.P. McCauley ‘Lady Madeline’s Dive’ in ThugLit Sept./Oct. [ebook] ‘Don’t kill me. Please don’t…’ ‘Knock it off’.