One of the Lost Tribes guys cited some literature that reversed the letters in "Damnoni" to get "Danmoni." That in turn allowed allowed the fanciful interpretation of "Dan's Mine" where "Dan" was one of the Hebrew Tribes which was according to those guys mining tin in Cornwall once upon a time. None of the more usual spellings work for that interpretation, of course, and if the Damnoni were the Picts it all sort of falls apart.