The passing of the name Tir Conaill into distant history has an unfortunate story behind it. The change commenced in the year 1584 when Sir John Perrott assumed the deputy Lordship of Ireland. Within a year, he had assembled a parliament in Dublin which, according to the Four Masters included the following Septs: Hugh O'Neill, chief of Tir Eoin; Hugh O'Donnell chief of Tir Conaill; John Og O'Doherty, chief of Inishowen; Turlough O'Boyle, chief of Boylagh and Owen O'Gallagher, O'Donnell's marshall.

The parliament passed a decree which stated that the area has to be known henceforth as Donegal (Fort of the Strangers). This measure was strenuously resisted by O'Donnell who refused to accept any interference in the running of Tir Conaill to the effect, he forbade the entrance of the English sheriff into his territory. However, by the time the Flight of the Earls had occurred some twenty years later, the name Donegal started to prevail in the vernacular.