 His nickname, "Dallán" ("little blind one"), was earned after he lost his sight, reputedly as a result of studying intensively.He was born in Maigen (now Ballyconnell), at the eastern edge of the territory of the Masraige of Magh Slécht in modern County Cavan.He was not a member of the Masraige but belonged to a branch of the Airgíalla called the Fir Lurg, who were in the process of spreading southwards into Fermanagh and Cavan.