Cairnín was Abbot of Iniscaltra, Lough Derg, County Donegal. He became an anchorite, and large numbers of people went to Lough Derg to seek him out. The Franciscan convent in Donegal preserved his manuscript, which contained a commentary on the 119th Psalm. It was then housed in Rome, but in 1871 was returned to the Dublin Franciscans. His feast day is 24th March.