 From the northern side, this pressure increased since the early 17th century with the rise of the Dar Fur Sultanate, as it established a patron-client relationship over the lowlands which became known as Dar Fertit.While "Dar" means "home of", "Fertit" does not describe any ethnic group, but was at the time a pejorative ""catch-all word for non-Fur, non-Arab, non-Dinka and non-Luo groups of Western Bahr El Ghazal"".Darfur historian Rex Sean O'Fahey describes the dynamic frontiers as follows