Green’s Dictionary of Slang

keg n.

also beer keg

1. (US) the stomach.

[US]F. Francis Jr Saddle and Mocassin 144: We’d been having ‘a time,’ and my keg was pretty full, too.
[US]College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 Keg (noun) A beer gut (usually on guys).

2. (Aus./N.Z.) beer, a barrel of beer [abbr. SE beer keg].

[Aus]Sport (Adelaide) 13 July 14/3: They Say [...] That Red H., the dashing ruck man for the Subs., has at last caught a tart, and will soon have to shell out the ‘keg’.
[US] in Randolph & Legman Ozark Folksongs and Folklore (1992) I 463: All you keg women, you better put it on the wall, / ’Cause I’m gonna get drunk an’ do my dirty talk.
[Aus]F.J. Hardy Outcasts of Foolgarah (1975) 192: Nothing like a keg party to drive away the blues.
[NZ]McGill Dict. of Kiwi Sl. 65/2: keg beer; from a barrel of beer.
[NZ]McGill Reed Dict. of N.Z. Sl. [as cit. 1988].
[US]F. Bill Donnybrook [ebook] Red suspenders going down over his keg belly.

3. (US drugs) 5 lbs of marijuana [? the amount of marijuana that would fill a beer keg].

[US]Current Sl. VI.

4. (N.Z. prison) a urine sample or its container.

[NZ]D. Looser Boobslang [U. Canterbury D.Phil. thesis] 98/1: keg n. a urine sample; a urine sample container.

In compounds

keg-belly (n.)

(Aus/US.) a distended stomach, the result of consistently excessive drinking.

https://www.outsideonline.com 1 Oct. 🌐 Doland cultivated a relationship with Harelson [...] often duct-taping a recorder and microphone to his beer-keg belly.
www.therenewalpoint.com 27 Mar 🌐 The fat that causes a ‘beer belly’ or ‘keg belly’ is mostly made up of a type of fat called visceral fat.
[Aus]D. Whish-Wilson I Am Already Dead 105: [T]he bartender, an older man with a drinker’s nose and keg-belly.
keg-legs (n.)

(UK juv.) an insult aimed at a girl with fat thighs or esp. calves.

OnLine Dict. of Playground Sl. 🌐 keg-legs n. derog unkind name shouted at girls with ‘fat’ calves or thighs or (more especially) calves.

In phrases

come off the keg

(Aus.) don’t talk nonsense.

[Aus]E. Dyson ‘The Picnic’ in Benno and Some of the Push 1: ‘Come orf the keg, little boy,’ replied the packer, with his man-of-the-world air. ‘You ain’t talkin’, y’ know; ye’re just makin’ a noise.’.
have a keg on board (v.)

(US) to be drunk.

[US]Lantern (N.O.) 21 May 2: Judging from the way Frank and his friend walked, they must have had a keg aboard.
keg it up (v.)

(N.Z.) to drink, usu. in a party or public house.

[NZ]Dominion (Wellington) 12 Sept. 1: Most of the group on the bus...had been ‘kegging it up’ since Friday celebrating the birthday of a one-year-old girl [DNZE].
M. De Chellis Mike D’s Awsome Drinkin Page 🌐 We will have a good time and keg it up yaaaaaaaaaa.
[NZ]McGill Reed Dict. of N.Z. Sl. 120: Students in particular engage in a keg party and compete in a keg race to consume the most beer in the shortest time, referred to as kegging it up. ANZ, from start of C20.
open a keg of nails (v.)

to open a bottle; thus to have a drink.

[UK]A. Binstead More Gal’s Gossip 176: Joe said he proposed to terminate the proceedings by opening just one keg of nails at the Carlton.
[US](con. 1948) G. Mandel Flee the Angry Strangers 31: Won’t you stay? We’re about to open a keg of nails.
[US](con. 1930s) C.E. Lincoln The Avenue, Clayton City (1996) 9: Lay a quarter on me [...] We might open a keg a nails.