Green’s Dictionary of Slang

quantum n.

[Lat. quantum, enough]

a drink.

[UK]Bridges Burlesque Homer (3rd edn) 57: Juno and he have had their quantum, / And play no more at rantum-scantum.
R. Newton Samples of Sweethearts and Wives! [cartoon caption] She’s got her quantum, by jingo!
[Aus]Mercury (Hobart) 23 Apr. 2/5: [from the Stranraer Free Press] [...] a quantum, a modicum, a thimblefu’.
[UK]Siliad 99: I, too, O comrade, quantum suff. would cry [F&H].