Traditionally, all of the major dialect-groupings of German dialects are typically named after so-called "stem duchies" or "tribal duchies" (German: "Stammesherzogtümer") by early German linguists, among whom the Brothers Grimm were especially influential. These tribal duchies came into existence at the end of the Early Medieval Period within the Holy Roman Empire and were thought to have been continuations of earlier tribal lands which were subjugated by the Franks and incorporated into their realm at the close of the Migration Period.