 Their territory lay in the baronies of Oneilland East and West in Co. Armagh, which both derive their name from the Uí Nialláin rather than the O'Neills.The Airthir kings of the Uí Nialláin sept ruled from Loch gCál (modern-day Loughgall).The Uí Bresail, also known as the Uí Bresail Airthir, ruled an area in northern Co. Armagh along the southern shore of Lough Neagh (in the barony of Oneilland East) before they were displaced by the lords of Clanbrassil, the MacCann's.