Green’s Dictionary of Slang

sling n.1

[SE sling, to throw (back)]

1. a draught, a ‘pull’ at a bottle or glass.

[US]J. May Journal and Letters (1873) 26: A case-bottle in his hand filled with Hollands, of which each of us took a sling .
Belfast Commercial Chron. 15 Dec. 4/2: Old Kentuck — I like to commence the evening in a lively manner. Major, let me have a leetle sling, but make it strong as thunder.

2. (Aus.) in monetary senses.

(a) (also slingback) a bribe, a gift.

[Aus]K.S. Prichard Golden Miles 74: ‘There’s some hungry bastards [...] makin’ big money on their ore, and never give the poor bugger boggin’ for them a sling back.’ The sling back might be ten bob on pay-day, or no more than a few pots of beer, but was always apprciated [AND].
[Aus]K. Tennant Joyful Condemned 232: Say I take twenty per cent of the cop for myself [...] all the rest goes in slings.
[Aus] ‘Whisper All Aussie Dictionary’ in Kings Cross Whisper (Sydney) xl 4/5: sling: A bribe.
[Aus]Bulletin (Sydney) 26 Apr. 44/1: They’re willin’ all right. Real brutal. Different if you beat it for the sling, but just for the no-roast is unreal ....
[Aus]R.G. Barrett You Wouldn’t Be Dead for Quids (1989) 9: They could afford to pay enormous slings to the police and politicians to keep the casinos operating.
[Aus]M.B. ‘Chopper’ Read Chopper From The Inside 80: Money for shady doctors, financing long-range campaigns, slings and backhanders.
[NZ]McGill Reed Dict. of N.Z. Sl. 192: sling A tip, bribe or bonus ANZ 1930s.

(b) a share of criminal gains.

[Aus]S.J. Baker in Sun. Herald (Sydney) 8 June 9/4: ‘Corner’ or ‘sling’ means a share in a haul; and ‘not a droob’ means nothing at all.

(c) a tip.

[Aus]R. Aven-Bray Ridgey-Didge Oz Jack Lang 11: The freight to Balmain had not left him with much shrapnel out of a deep-sea-diver. The driver did not get a sling.
see sense 1.
see sense 1.