From: Christopher Gwinn
> It is most like related to the Irish words bag "combat", andhas
> bagach "combative", as well as Middle(?) Welsh kymwy (*com-bag-
> ) "affliction", and likely meant something like "combatants". It
> the same suffix as Gaulish alauda "lark" (alouette) and bascauda.Forgot to add - Pokorny relatesBagaudae to PIE *bhe:gh- / bho:gh-
> See Xavier Delamarre's "Dictionnaire de la langue gauloise" (which
> is the best resource for Gallo-Brittonic etymologies right now).