According to Lambert McKenna (pp.xvi-xvii): "[They] probably acquired their land in Connacht as a reward for military service rendered to the tribes which had victoriously invaded that part of the country.
According to this story, the Luighne accompanied Tadhg mac Cian, who "The genealogists brought Tadc and his descendants from Éli in northern Munster, but since we find the Luigni and Gailenga closely associated as neighbours and allies in Connacht ... there is reason to agree with MacNeill that they were vassal tribes of fighting men whom the Connachta and Ui Neill ... planted on the lands they had conquered" (IKHK, p. 69) Of the original Brega-based tribes called Gailenga, Luigni, Saitne, Delbhna, Ciannachta, Francis John Byrne goes on to say: "the Brega peoples of that name ... extending as they did in a group of tribal kingdoms from Glasnevin to Lough Ramor in Cavan, give the impression of a remarkably homogeneous body.
But the Boyne valley had been an area of settled culture since Neolithic times, so that it is likely that a basic unity persisted under the superstructures of succeeding conquests."
Byrne notes that the Luighne dominated smaller, minor tribes (including the likes of the Calraige, Grecraige and Corca Fhir Trí), "and have some claim to be considered an over-kingdom, as was recognised in the 12th century when their lands were erected into the diocese of Achonry."
Hence it would appear probable that the territory afterwards called Gallen was at first ruled by its Gaileanga princes, and that towards the end of the 10th century it came under the power of the chieftains of Luighne, chiefly that of the Í Ghadhra, who ruled it till the early 13th century when they were thrust aside by the Jordans; it is often afterwards referred to as Mac Jordan's country."