An alternate theory suggests that speakers of Proto-Armenian were tribes indigenous to the northern Armenian highlands, such as the Hayasans, Diauehi, and/or Etiuni. Although these groups are only known only from references left by neighboring peoples (such as Hittites, Urartians, and Assyrians), Armenian etymologies have been proposed for their names. While the Urartian language was used by the royal elite, the population they ruled was likely multi-lingual, and some of these peoples would have spoken Armenian. This can be reconciled with the Phrygian/Mushki theory if those groups originally came from the Caucasus region or Armenian Highlands.