Green’s Dictionary of Slang

1. (Aus.) fifty lashes.

1847

[A. Harris] (con. 1820s) Settlers & Convicts 26: A mad had several ‘fifties’ on consecutive days, to compel him to confess a robbery.

2. (US) a $50.00 bill.

1907

Wenatchee Dly World (WA) 30 Sept. 4/2: He would carelessly fish out [...] a large Wad of the Green Kind with a Fifty for a Wrapper.

3. (Aus.) a pint of beer composed of 50% old beer and 50% new.

1960		‘Nino Culotta’ Cop This Lot (1965) 147: ‘Wouldn’ mind bein’ there now, but. Long cold schooner o’ fifty, eh?’.
1971		F.J. Hardy Outcasts of Foolgarah (1975) 82: Five schooners of fifty, thanks, love.
1972		J. O’Grady It’s Your Shout, Mate 44: ‘I tried ’em all - new an’ old and fifty fifty an’ what have you’.
1978		R. McLelland Outback Touring 121: In New South Wales some pubs have both old and new beer on tap [...] A ‘fifty’ is a 50-50 combination of new and old, i.e. half a glass from one tap and half from the other [AND].
2011		B. Fingerton in Rock the Bloody Boat! 31 Aug. 🌐 [blog comment] I remember a lot of old blokes drinking fifty.

4. (US drugs) a packet of a drug worth $50.

1977		N.C. Heard When Shadows Fall 161‘: Wanna sell me a fifty?’ [...] ‘Sucka,’ he drawled at J.B., ‘I ain’t no dope dealer. I sniff coke, not sell it’.
1989		(con. 1982–6) T. Williams Cocaine Kids (1990) 47: I’m gonna make up all the twenties, the fifties [$20 and $50 packets].

5. (US black) the police [five-oh n.].

2000

P. Beatty Tuff 174: Fifty came in and blew up the spot, next day my shit was ghost.

6. (N.Z. prison) an insult, a stupid person [the insignificance of the sum of 50 cents].

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 68/1: fifty (also fifty cents) n. an unintelligent inmate: ‘Hey, fifty! Come over here!’.

7. a £50.00 note.

2011

J.J. Connolly Viva La Madness 19: Swigging pints of D.P. and lighting fat crigars with a fifty.