Green’s Dictionary of Slang

a drink, esp. in a ‘medicinal’ context.

1867		M. Lemon Golden Fetters III 35: Come, sit down, and have an ‘alleviator’.
1884		Eve. News (Sydney) 27 Oct. 8/3: William Traves and James Fitzgerald felt a touch of that perpetual thirst which usually torments the votaries of Bacchus; but they had not the wherewithal to procure an ‘alleviator’.
1923		J. Manchon Le Slang.
1933		‘William Juniper’ True Drunkard’s Delight.
1945		Baker Aus. Lang.
1962		(con. WWII) J.O. Killens And Then We Heard The Thunder (1964) 427: ‘How’s about a little alleviation?’ [...] he took a bottle from his hip pocket.