High Quality Content by WIKIPEDIA articles! The O'Neill dynasty is an important collection of families that have held prominent positions and titles throughout European history. The O'Neills take their name from Niall Glúndub, an early 10th century High King of Ireland from the Cenél nEógain. Confusion then arises because the Cenél nEógain, descendants of Eógan mac Néill, were a branch of the Uí Néill dynasty who took their name from Niall of the Nine Hostages, a legendary 5th century High King of Ireland. The Uí Néill were in turn a branch of the Connachta, descendants of the legendary Conn of the Hundred Battles, son of Fedlimid Rechtmar, son of Tuathal Techtmar.