Green’s Dictionary of Slang

1. (also wrong) a criminal; in weak use, an undesirable person.

1938		J.H. O’Hara Hope of Heaven 139: If I ever saw a wronggo, that Henderson is it .
1947		B. Schulberg Harder They Fall (1971) 18: I liked the way she had been about Sailor Beaumont, even if he was a wrongo.
1959		W. Burroughs Naked Lunch (1968) 180: His dossier contains three pages of monikers indicating his proclivity for cooperating with the law [...] Ali the Stool, Wrongo Sal, The Wailing Spic.
1968		K. Brasselle Cannibals 37: If she pegged someone as a wrongo, believe me, he turned out to be just that.
1969		Punch 12 Nov. 801: Deploring the good-guys-and-wrongs syndrome of US foreign policy.
1979		F. Norman Too Many Crooks Spoil the Caper 61: I stick my neck out for you by vouching for your not being a wrongo.
1985		‘Derek Raymond’ Devil’s Home on Leave 163: I’ve had my eye on both of you [...] and you look like a couple of wrongos to me.
1990		(con. early 1950s) J. Ellroy L.A. Confidential 219: Two wrong-o’s who couldn’t walk a straight line.

2. a mistake, error or lie.

1937		J. Curtis You’re in the Racket, Too 264: Never brought you nothing that was a wrongo yet, did I?
1938		W. Winchell On Broadway 19 Mar. [synd. col.] When I have a ‘wrongo’ the wires services never fail to say so.
1942		W. Winchell ‘On Broadway’ 26 Mar. [synd. col.] That rumor about the Army transforming the Roney into a hospital is a wrongo.
1953		A.J. Liebling Honest Rainmaker (1991) 107: Shaving the odds and occasionally slipping them a wrongo.
1957		‘Ed Lacy’ Lead With Your Left (1958) 101: If this turned out to be a wrongo [...] Hell, they could only hang me once.