[2] Tirkeeran derives its name from the territory of the Airgiallan clan Ui Mhic Carthainn (MacCarthain), one of the earliest tribes in the area based to the south-east of Locha Febail (Lough Foyle).

It was around this period that the Cenél nEóghain were attempting to expand eastwards from their homeland in Innishowen, in modern-day County Donegal and into central Ulster.

[4] Eventually, the Cenél nEóghain crushed the power and independence of the Uí Mhic Carthainn and subjugated them; however, it would remain in some minor form until the end of the 11th century, when the Annals cite "Conchobhor ua hAinniaraidh, king of Cianachta and Ua Cein king of the Ui Meic Carithinn fell by each other in combat".

[6][7] When the baronies of Ulster were being created by the English from 1585, the general manner was to name it after the principal town or castle lying within the area, in which they held their court, baron, and jail.

The 1591 inquisition which shired County Tyrone specified as one of its eight baronies "Anagh, conteyninge [containing] Tyrchyrine [Tirkeeran], Sgryn [Magilligan], and Clandermod [Clondermot]".