Abbr. often preceding 29-Down

• Letters on an invitation
• [Guests must provide their drinks]
• Invitation reminder letters
• Party directive, briefly
• Abbr. in many a party invitation
• Inits. on a party invitation
• "We're not supplying liquor"
• Part of an invitation to an imbiber
• "We're not serving liquor," on invites

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
initialism (acronym) for "bring your own bottle" or "bring your own booze," by 1951.