Son of Tulchan, an Ulster saint, d. at Taghmon, 636. He founded his celebrated abbey at Taghmon (Teach Munnu) in what is now County Wexford, in 599. He is principally known as the defender of the Irish method of keeping Easter, and, in 630, he attended the Synod of Magh Lene, at which he dissented from the decision to adopt the Roman paschal method. Another synod was held somewhat later at Magh Ailbe, when St. Fintan again upheld his views in opposition to St. Laserian (Mo Laisre). But the views of the University Church prevailed. His feast is observed on 21 October. The beautiful stone cross of “St. Munn” still stands in the churchyard of the village.
From the Catholic Encyclopedia