What is the X in X-mas?
late 14c., "soiled, dirty, filthy," from bawd + -y (2). Meaning "lewd" is from 1510s, from notion 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]