"of or pertaining to sale, sales, or the business of selling," word-forming element from genitive of sale (n.), by 1520s, in salesman. Cf. saleswork "work done for sale" (1775). For earlier use of similar formations, compare craftsman, oarsman, both Middle English. Sales tax is attested by 1886; sales clerk by 1863; sales associate by 1946. Sales representative is from 1910.