One story has it that they were so called because they had been made to carry bags of earth during their enslavement. The Firbolg are credited with the division of the island into three, and then five, provinces or coiceds and establishing a sacred kingship based on the relationship between the king’s integrity and the land’s fertility. The provinces would become Ulster in the north, Connaught in the west, Munster in the south, Leinster in the east, and Tara, the place of the king, in the center.

A golden age of the Firbolg lasted only thirty-seven years before the arrival of the Tuatha de Danann, a group of “invaders” who are the pre-Celtic equivalent of a pantheon of Irish mythology.