Prov. Hainaut [Henegouwen], mainly within the triangle Ronse [in prov. East-Flanders] - Leuze - Ath (Flemish: Aat), i.e. in Buissenal, Frasnes-lez-Buissenal, Grandmetz, Mainvault, Moustier, Œdeghien, and Ostiches, but also in Bon-Secours, Naast (Walloon: Nåsse), Péruwelz and Rœulx (near Soignies [Flemish: Zinnik]); NB: According to Boone, "fou is a derivative of Latin follis (bag or bellows)", adding that Old French fol can also signify "musical instrument".