In Irish mythology, Ireland was once inhabited by the Fir Bolg, who were descended from the earlier Muintir Nemid. The Fir Bolg were later defeated by another group of Nemed's descendants known as the Tuatha Dé Danann in the Battle of Cath Maige Tuired. However, the victors gave the Fir Bolg a quarter of Ireland to live in. According to Wikipedia,
[T]he Tuath Dé offer them one quarter of Ireland as their own; they choose Connacht and are mentioned very little after this in the myths.
The races that occupied the land when the so-called Milesians came, chiefly the Firbolg and the Tuatha De Danann, were certainly not exterminated by the conquering Milesians. Those two peoples formed the basis of the future population, which was dominated and guided, and had its characteristics moulded, by the far less numerous but more powerful Milesian aristocracy and soldiery.
So what happened to the Fir Bolg ultimately? When were they last mentioned as a distinct identity?