also sell-out, "corrupt bargain," 1862 (in Mary Chesnut's diary), from the verbal phrase (at that time often meaning "dispose of one's interests" in a company, etc.), from sell, v. + out, adv.. Meaning "event for which all tickets have been sold" is attested from 1923. The verbal phrase sell out "prostitute one's ideals or talents" is attested from 1888.