Green’s Dictionary of Slang

1. (Aus., also niner) a 9-gallon (41-litre) keg of beer.

1880		Bulletin (Sydney) 3 Apr. 1/4: A young lady of Darlinghurst says she never stands upon trifles. No! but she stands upon small nines.
1927		Record (Melbourne) 26 Feb. 8/2: Senior Constable Burroughs raided the premises of Mr. Britton at Port Melbourne, and found four ‘nines’ of beer, a bottle of whisky, and men inside, and men running away.
1944		Argus (Melbourne) 11 Mar. 2/3: It was their beer night in the mess (they get it twice a week), and by fraud, chicanery, and misrepresentation they’d managed to land a 27 gallon beer keg instead of the usual niner.
1957		‘Nino Culotta’ They’re a Weird Mob (1958) 89: ‘How c’n ut be a good night without women?’ Pat said. ‘There’ll be a coupla nines.’ ‘Aw well that’s different. Women’ll keep.’ [Ibid.] 107: Who’s bringin’ the niners?
1962		Hogbotle & ffuckes Snatches and Lays (1973) 5: Without a crowd of mates and a niner or its equivalent this book would be a dead loss, as useless as a cookery book to a man marooned on a barren rock.
1964		B. Hesling Dinkumization or Depommification 81: Frank had managed to get a ‘nine’ [...] by following a brewery dray in a taxi biding his time.
1977		J. Ramsay Cop It Sweet 63: NINER: Barrel of beer containing nine gallons.

2. (US, also milly, 9, nine-mil, nine-millie, nine-milly, nines) a 9mm pistol.

1987		Boogie Down Productions ‘Super Hoe’ 🎵 If you’re a guy, a nine’ll do the trick.
1988		Ice-T ‘Drama’ 🎵 Pipe bomb in my trunk, got a nine in my lap.
1988		H. Gould Double Bang 232: A Thirty-eight and a nine mil.
1994		UGK ‘Return’ 🎵 Say hello to the nine milly (Buck!) millameter (Buck! Buck!).
1997		Simon & Burns Corner (1998) 72: Almost hoping they come back on him, figuring he’ll go to his nine and catch himself a body.
1997–2000		College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 9-millie (noun) 9 mm gun. [Stamford, CT].
1999		Dr Dre ‘Some L.A. Shit’ 🎵 Fuck a scrap in killa Cali, AK’s and 9’s.
2002		50 Cent ‘Wangsta’ 🎵 What make you think I wont / Run up on you with the nine.
2006		Simon & Burns ‘Alliances’ Wire ser. 4 ep. 5 [TV script] Nine? Nah. Too much buck. Prob’ly a 40 cal.
2007		Guardian 25 Aug. 🌐 It was only a milly, a nine milly. They pointed the gun to my head.
2007		UGK ‘Trill Niggaz Don’t Die’ 🎵 I pack that nine everytime, and I ain’t trying dying.
2013		A$AP Rocky ‘Suddenly’ 🎵 Ricky had a deuce-deuce, two shotty pumps with a baby 9.
2013		K. Koke ‘Bring Me Down (Intro)’ 🎵 Police are tryna bring me down (down) / They don’t wanna see me rise up (up) / That’s why I lift my nine up (up).
2018-20		T. Thorne (ed.) ‘Drill Slang Glossary’ at Forensic Linguistic Databank 🌐 Milly - a 9mm pistol.
2019		S.M. Jones Lives Laid Away [ebook] ‘That nine-milly you’re carrying? Keep it stowed, lover, or someone might get hurt’.
2019		D. Winslow Border [ebook] Cirello has his nine at his waist and another weapon, a .380 throwaway, strapped to his ankle, and a Mossberg 590 shotgun under a coat.
2021		T. Pluck Boy from County Hell 195: Dropped the shotty ans drew the nine.

3. (UK black/drugs) nine ounces of crack cocaine.

2016

Harlem Spartans ‘Hazards’ 🎵 GT stepped in with a 252 that's a nine in O’z (nine).