bar + back, due to working in the back area of the bar (not interacting with patrons), reinforced by “to have someone’s back” meaning “to support, assist someone”. Compare back of house and back office.
barback (plural barbacks)
- (bartending) An assistant to a bartender
2000 December 1, Jack Helbig, “Reindeer Games”, Chicago Reader:
- Cerda moved to Chicago and worked at a series of bars and clubs: the Orbit Room, the Paradise Club, even a stint at Limelight, where he supplemented his earnings as a barback by performing as Nina Hagen in one of the cages.
- runner (Britain)
- To work as a barback.