late 14c., "soiled, dirty, filthy." Meaning "lewd" is from 1510s, from bawd (q.v.), with sense of "pertaining to, or befitting a bawd;" usually of language (originally to talk bawdy).
"Bawdy Basket, the twenty-third rank of canters, who carry pins, tape, ballads and obscene books to sell." [Grose, "Dictionary of the Vulgar Tongue," 1785]