On party invitations:BYOB
A. Technically, 
events at which guests are asked to bring or pay for food or... [DOC] [TLE] Invitation Wording for Bringing Something to the Party ... [PAR] Alcohol is expensive, so it is not uncommon for party invitations to ask guests to ... 
do so is to add BYOB, or Bring Your Own Beer, at the bottom of the invitation.