Stories We Like: A Guide to the Comma
late 14c., "force-meat, stuffing;" 1520s, as a type of dramatic work, from Middle French farce "comic interlude in a mystery play" (16c.), literally "stuffing," from Old French farcir "to stuff," (13c.), from Latin farcire "to stuff, cram," of unknown origin, perhaps related to frequens "crowded."
The pseudo-Latin farsia was applied 13c. in France and England to praise phrases inserted into liturgical formulae (e.g. between kyrie and eleison), then in Old French farce was extended to the impromptu buffoonery among actors that was a feature of religious stage plays.