Daig (d. 587), son of Cairell, founder and first bishop of Inis Caín and a saint in the Irish tradition, is traced by the genealogists to the Uí Néill dynasty of Cenél nÉogain. His father is named as Cairell son of Laisre Lond, a descendant of Éogan (qv) son of Niall Noígiallach (qv); his mother is alleged to have been Deidiu daughter of Trian, which if true would make him a half-brother of Diarmait (qv) of Inis Clothrann and a great–grandson of Dubthach (qv) of the moccu Lugair. In his own Latin Life, Daig, whose name signifies ‘fire’, is assigned a sister Lasair; her name, like that of their grandfather Laisre Lond, means ‘flame’. These names, in the context of several episodes from the Life, suggest pagan solar symbolism, but also Christian pentecostal symbolism. According to the genealogies, Daig had another sister, Feimme, who also followed the religious life.
Hagiographical tradition makes Daig a student of Finnian (qv) of Clonard, a distinction he shared with many others including Mauchteus (qv) of Louth. The hagiographers stress Daig's role as a craftsman, doubtless representing him as a model for metalworkers of their own day. He is credited with having produced a wide range of metal artifacts including bells, crosiers, and reliquaries, and is said to have been artisan to Ciarán (qv) of Saigir. Subsequently, Daig founded his own church at Inis Caín (Inishkeen) which, although located by the sources in the territory of Conaille Muirthemne, is in the present Co. Monaghan. He attained the grade of bishop, and is featured in the tract ‘De episcopis’. Daig is accorded a reputation for learning, being acclaimed as a scribe and as the teacher of Berach (qv) of Cluain Coirpthe. He is represented as the spiritual director of several communities of women in the hinterland of Inis Caín.
Daig, it is claimed, outlived his older contemporary, Mauchteus, bringing the latter the viaticum on his deathbed. His own death is assigned to 587, the date according to the martyrologies being 18 August. Inis Caín long survived as an ecclesiastical centre; it appears that there was a mill and probably a sizable community at the site. The next recorded abbot of Inis Caín is Flann grandson of Dachua (d. 771).