Green’s Dictionary of Slang

(Aus./US) bring your own, refers to bringing drinks to a party or an unlicensed restaurant; thus in ext. use to refer to anything other than alcohol; var. uses: b.y.o.b., bring your own bottle or booze; b.y.o.g., bring your own grog; b.y.o.l., bring your own liquor.

1959		L.P. Boone ‘Gator Sl.’ AS XXXIV:2 155: If they decide upon a party, they throw a ball [...] in some cases, a BYOB (bring your own bottle).
1967–8		Baker et al. CUSS 73: B Y O B / Bring your own bottle, bring your own booze / A drinking party.
1968		‘Sl. of Watts’ in Current Sl. III:2 13: BYO, v. bring your own. Used at parties to encourage guests to bring their own liquor meaning the wine you take to an unlicensed restaurant.
1969		in Current Sl. IV:3-4 (1970).
1972		Sat. Rev. (US) 24 June 18: The dance was held in the game room of the rec center—where else? Music was provided by a local group called the Mixed Bag, admission was $1 per person, b.y.o.b.
1986		C. Bowles G’DAY 75: A lot of these places are B.Y.O. so you Bring Your Own grog, often in your own Esky.
1992		K. Lette Llama Parlour 17: It must have been a BYO Dog party. Each actress had a little mohair poodle tucked under her arm.
1996		Penguin Bk of More Aus. Jokes 314: The Irishman went to a brothel, and, seeing a BYO sign on the door, went home to get his wife.
1998		M. Baker Bad Guys 30: They had a party after a basketball game, BYOB.
2002		Flying E Ranch (Wickenburg AZ) brochure 🌐 No bar, a B.Y.O.L. social hour, ice and mixes furnished, and always exotic tasty appetizers.
2002		Old Mogo Town Gold Rush Theme Park 🌐 Diggers Tavern open all day for morning, afternoon teas and lunch great menu and B.Y.O.G.
2003		McGill Reed Dict. of N.Z. Sl.
2003		N. Green Angel of Montague Street (2004) 15: Nice Greek place [...] cheap, BYOB.
2010		L. Redhead Thrill City [ebook] The reception [was] at a Turkish BYO restaurant on Syudney Road.