bring your own bottle, as of liquor or wine: often included in an invitation to indicate that the host will not provide liquor.
Origin of BYOB
First recorded in 1970–75
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Australian and NZ an unlicensed restaurant at which diners may drink their own wine, etc
Word Origin for BYO
C20: from the phrase bring your own
bring your own beer
bring your own booze
bring your own bottle
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
initialism for "bring your own bottle" or "bring your own booze," by 1951.
Online Etymology Dictionary, © 2010 Douglas Harper