Yours, Etc.: Origins and Uses of 8 Sign-Offs
late 14c., "good or noble deed," also "advantage, profit," from Anglo-French benfet "well-done," from Latin benefactum "good deed," from bene facere (see benefactor). Meaning "performance or entertainment to raise money for some charitable cause" is from 1680s.
late 15c., from benefit (n.). Related: Benefited; benefiting.