mousseron

mousseron is masculine in French.

St. George's mushroom (Calocybe gambosa)

Inherited from Middle French mouceron, from Old French moisserun, moisseron (compare Late Latin mussirio, Occitan mossalon, Catalan moixernó), of uncertain origin: * Probably ultimately derived from Old French mosse, moise (“moss”), of Germanic origin, from Old Dutch *mos, from Frankish *mos, from Proto-Germanic *musą, as the type of fungus so-named applied to one which grows in moss. * Klein and Watkins prefer a pre-Roman substrate origin, if the earlier form was something like Vulgar Latin *mu