From The Art and Popular Culture Encyclopedia
Facetus is Latin for:
The word facetus became known in the Renaissance in the form of facetia, jest or joke. In its plural form it became associated with collections of witty tales, best known of which are the Facetiae by Poggio.
- Treating serious issues with deliberately inappropriate humor; flippant
- Pleasantly humourous, jocular
1592, from Fr. facétieux, from facétie "a joke," from L. facetia, from facetus "witty, elegant," of unknown origin, perhaps related to facis "torch." It implies a desire to be amusing, often intrusive or ill-timed. " in booksellers' catalogues, is, like curious, a euphemism for erotica." [ Henry Watson Fowler ] --etymonline