Green’s Dictionary of Slang

in card-games, to stack the cards in a certain way to facilitate cheating; also fig. use.

1851		‘Losing Game of Poker’ in Burke Polly Peablossom’s Wedding 48: You know the cards were stocked, so as to give you the hand you held.
1864, 1867, 1870		Hotten Sl. Dict. 247: To stock cards, is to arrange cards in a certain manner for cheating purposes.
1868		G.W. Harris ‘Early Life of Sut Lovingood’ Knoxville Daily Press and Messenger III 7 May in Inge (1967) 299: Sugartail Lovingood, was a son ove his daddy, and bein’ my daddy is tharfoar gran’ daddy to ‘my son’ Sut – That is, if thar was no stockin’ ove kerds.
1887		G. Devol Forty Years a Gambler 12: He was well posted on cards, and taught me how to ‘stock a deck,’ so I could give a man a big hand.