Green’s Dictionary of Slang

1. to steal, to embezzle.

1833		T. Hamilton Men and Manners II 387: One member of Congress [...] was charged with selling franks at twopence apiece, and thus coppering his pocket at the expense of the public [DA].
1884		(US newspaper ) Aug. n.p.: He’s been in office for a long while an’ never coppered a d——n cent [DA].
1906		Houdini Right Way to Do Wrong 38: A single "plant" on a Chicago bank was pulled off recently, whereby the clever swindler coppered out $30,000 for himself with very little effort.

2. to kill.

1897

A.H. Lewis Wolfville 55: Still Enright’s all-wise enough to copper the Greaser.

3. to outwit, to spoil.

1878		J.H. Beadle Western Wilds 46: He staked a pile of ‘chips’ and won; then made and lost, and made and lost alternately, selling his stock when ‘broke,’ [...] till the tail of his last mule was ‘coppered on the jack’.
1883		‘Mark Twain’ Life on the Mississippi (1914) 268: The safe way [...] is to copper the operation, and at the same time buy enough property in Vicksburg to square you up in case they win.
1897		A.H. Lewis Wolfville 99: The victim [...] don’t copper the play by makin’ vain remarks, but brings his gatlin’ into play surprisin’. [Ibid.] 330: Of course, I’m heap interested in this yere snake knowledge [...] But it sorter coppers my appetite.
1905		R. Beach Pardners (1912) 57: I’d sure copper this move and play her to lose.
1913		Van Loan ‘The Good Old Wagon’ Lucky Seventh (2004) 206: Your wrist was cut, but I’ve got that bet coppered.
1922		P.A. Rollins Cowboy 80: Faro’s terms permitted one puncher to ‘keep cases’ on another man [...] and further permitted this puncher, if dissatisfied with these actions or plans, to ‘copper’ them by initiating a diametrically opposite sort of performance or scheme.
1931		M. Harris ‘Facing the Mob’ in Gangland Stories Feb. 🌐 You’ll have a sweet time explaining to the other gangs how come you wasn’t bumped off when Bad News coppered your bet.
1932		Z. Grey Robbers’ Roost 218: Wal, you coppered it with the ace.

4. to obtain, to make sure of getting.

1871		Galaxy (N.Y.) July 57: ‘Who’s payin’? I’m dead broke?’ ‘What! Cleaned out?’ ‘You bet. But if that dealer hadn’t railroaded, I’d a got square copperin’ the ace.’.
1891		A. Day Mysterious Beggar 264: If you’re a bit skeery, then ’till the thing’s well coppered, you can nark ’round on the sly.
1901		W. Irwin Love Sonnets of a Hoodlum XX n.p.: All the chronic glad hand-claspers came To copper invites for the wedding day.
1916		J. Lait ‘Canada Kid’ Beef, Iron and Wine (1917) 151: A lotta judges is tryin’ to copper the lowdown on the bad boy problem.
1929		C. Coe Hooch! 49: He won’t waste any time gettin’ to Swinnerton an’ that’s the little bet I’ll copper!
1936		R. Chandler ‘Guns At Cyrano’s’ Red Wind (1946) 237: He tried to copper his bet on your blackmail racket.
1950		Sugarfoot [film script] In this game you can’t copper no bets [W&F].
1968		(con. mid–late 19C) S. Longstreet Wilder Shore 34: Coppering your bet (a six-sided black chip on top) is a no bet.

5. (US) to hedge a bet so as to minimize possible losses; in fig. use to distrust.

1900		Nat. Police Gaz. (NY) 3 Nov. 11/3: When he talks it’s pretty safe to copper all he says.
1929		D. Hammett Red Harvest (1965) 50: ‘The dive is off. Better copper your bets while there's time’.
1959		(con. 1900-29) L. Katcher Big Bankroll 55: Rothstein was coppering part of the bet. He owned a piece of the business and the money the spectators would spend would yield him a profit.