From the descendants of Eoghan, son of Niall of the Nine Hostages in the fifth century, together with his brothers Conall Gulban and Eoghan, conquered the land of northwest Ulster: which was then divided between them, Tirowen and Tirconnel. Many of the early kings of Ulster through the centuries were of the Dál n-Araidhe and the Dál Fiatach clans of counties Armagh, Down and Antrim. The three Collas branch off to warrior classes, sons from Ulster, Kings of Oriel, and one branching off to Ó Neill from a marriage of Gaul to Connacht and rivaled yet by the Three Collas. In later times The Ó Neills assumed the heraldic emblem of the ancient Kings of Emania which was, The Red Hand of Ulster; together with the battle-cry of Lamh-dearg Aboo or the Red Hand for Ever.

The Leabhar na gCeart cites the people of Aradh were Rudricians, descended from Feartlachta, son of Fearghus, King of Ulster, in the 1st century... akin to the Uí Tuirtre of South Derry and the North Albans of Antrim... but these people were driven out by the descendants of Eoghan, son of Ailioll Óluim, and thereafter the territory was called Eoghanact Aine Cliach. Eoghan captured the stronghold at Aileach and his kingdom included the penninsula known as Inishowen (Inish Eoghain) in Donegal. The Cenél Eoghain of the Donegal-Tirowen division were one of the main branches of the Northern Uí Neill. The Tirowen territory comprised Tyrone and part of Derry and Tir Eoghan meaning ‘Eoghan’s country.’ By the 13th century the O'Donnells rose to dominance among the Donegal septs of Cenél Conaill, the O'Gallaghers becoming the leaders of the O'Donnell calvary and MacDonnells of the Hebrides landing in Antrim and Derry.