[people of Lug (?)]. Early Celtic people who invaded Ireland before the advent of written records, giving their name to the province of Leinster. They were placed second in the order of Celtic invaders, after the Érainn. They settled not only in what is now Leinster but also in other parts of the island, including large portions of Connacht. Thomas F. O'Rahilly (1946) argued unconvincingly that they were a P-Celtic people and only adopted genealogies implying a Q-Celtic origin after the dominance of the Goidels in Ireland. Their ancestor deity, Labraid Loingsech, was thought to have invited 2,200 foreigners back with him from the continent of Europe, who became the Lagin. According to their own invasion legend, they were Gaulish in origin and invaded Ireland from Brittany (Armorica). The Annals of the Four Masters set this after 431 bc, the Book of Leinster after 307 bc. Contemporary scholarship suggests a much earlier date. They brought with them the Domnainn and the Galióin.
See Thomas F. O'Rahilly, Early Irish History and Mythology (Dublin, 1946), 17–24, 101–20;Alfred P. Smyth, Celtic Leinster (Dublin, 1982).