Green’s Dictionary of Slang

f.y.o. n.

[abbr. fill your own; i.e. a beer flagon]

(N.Z.) an invitation to a party at which the guests are asked to supply the drink.

Contact (Wellington) 5 Dec. 4: [advert] Dominion Tavern Bottlestore F.Y.O. 2 Ltr Flagons Lion brown $4.70 [DNZE].