Your Irish Ancestry: Kennedy (1992) VHS
The O’Kennedy family (Irish: Ó Cinnéide), sometimes Kennedy, were an Irish royal dynasty, a sept of the Dál gCais, founded in the Middle Ages who were Kings of Ormond. Their founder was the nephew of High King Brian Boru (1002–1014). The name Cinnéide belonged to Brian Boru’s father Cennétig mac Lorcáin, King of Thomond, in the tenth century AD. (Brian Boru was an Ard Rí or High King of Ireland). The Kennedys did not descend directly from Brian Boru, but from Cinnéide’s eldest son Donncuan. Donncuan’s son Mahon was the first to call himself Ó Cinnéide which is Irish for grandson of Cinnéide.
According to historian C. Thomas Cairney, the O’Kennedys were one of the chiefly families of the Dal gCais or Dalcassians who were a tribe of the Erainn who were the second wave of Celts to settle in Ireland between about 500 and 100 BC.
Placenames such as Killokennedy in Thomond are indicative of their longstanding presence in the region.
Credit to : Irish Medieval History