Green’s Dictionary of Slang

a general invitation to have a drink.

1889		‘’Arry in Parry’ in Punch 29 June in P. Marks (2006) 95: Wot’s yer pison, old pal?
1897		People’s Cyclopedia 3010: ‘What’s your poison?’ Is often heard as an Invitation to drink.
1898		W.A. Sun. Times (Perth) 16 Jan. 7/1: What’s your poison, gents?
1900		Bulletin (Sydney) 27 Jan. 19/2: What’s your poison, mister? And yours? Two whiskies. Yours? Soda-and-b.
1908		Bulletin (Sydney) 13 Aug. 14/2: ‘What’s yer nourishment?’ [...] / ‘Mine’s a beer.’.
1910		P. Mighels Furnace of Gold 107: ‘What’s your poison?’ ‘Nothing, thank you,’ answered Bostwick.
1922		G.B. Burgin More Memoirs 265: ‘Say, what’s your poison?’ ‘Nothing, thanks; too early in the evening’.
1933		‘William Juniper’ True Drunkard’s Delight.
1963		G. Lambert Inside Daisy Clover (1966) 205: What’s your poison, Daisy?
1967		J. Wynnum I’m a Jack, All Right 48: ‘What’s your poison?’ ‘The usual’.
1979		T. Wiseman Game of Secrets 325: ‘What’s your poison?’ Tiviello inquired. ‘Nothing.’ ‘Mind if I do?’ He proceeded to make himself a white lady.
1989		T. Blacker Fixx 146: What’s your poison, Collers?
1992		R. Price Clockers 141: What’s your poison there, Sean?
2012		J. Mear Mechanisms of Desire 172: ‘What’s your poison?’ ‘Some single malt, neat’.
2019		N. Walker Cherry 191: ‘Lemme buy all you men a round, okay? How about that?’ We said that would be great and thank you. ‘What’s yer poison?’.