In the Early Middle Ages, Brittany was divided into three kingdoms—Domnonée, Cornouaille (Kernev), and Bro Waroc'h ("Broërec")—which eventually were incorporated into the Duchy of Brittany. The first two kingdoms seem to derive their names from the homelands of the migrating tribes in Britain, Cornwall (Kernow) and Devon (Dumnonia). Bro Waroc'h ("land of Waroch", now Bro Gwened) derives from the name of one of the first known Breton rulers, who dominated the region of Vannes (Gwened). The rulers of Domnonée, such as Conomor, sought to expand their territory, claiming overlordship over all Bretons, though there was constant tension between local lords.