This verse was written in a text of Féineachas ('Brehon Law') in the 8th Century:
Batar trí prímcheinéla i nHére, .i. Féini 7 Ulaith 7 Gáilni .i. Laigin.
There were three primary kinships in Ireland, i.e., the Féini and Ulaidh and Gáilióin, i.e., the Laighin.
These three kinships which have been remembered for two millenia through poems and stories, have been associated in recent times with four ancient Iron Age sites located in the central area of Ireland.
Almost all Gaelic manuscripts and all Catholic records were destroyed by the Gall (foreigners) from the Norman invasion of Ireland in 1169 until 1782 and the liberal period of Grattan's Parliament.
There are only a few sources of population records before then and no real surviving census until 1901.