St Nessan is reputed to have founded the monastery in Mungret. St Nessan was also known as St Nessan the Leper, and he was a disciple of St Patrick according to local folklore. However, St Nessan died in 551 or 561 and so this makes it extremely unlikely that he could ever have been a disciple of Patrick. Nessan may have been a disciple of St Ailbe from Emly.
In his book 'Portrait of Limerick', Mainchín Seoighe relates a
tale of how St Nessan met St Patrick, and went on to become the founder
of Mungret monastery.
Just then a youth named Neassán appeared carrying a cooked ram on his back for the feast. His mother accompanied him. Patrick asked Neassán for the ram and Neassán gave it to Patrick against his mother's wishes. Patrick then gave the ram to the jugglers and instantly the ground opened and swallowed them. Patrick cursed Lómán and Mantán and baptised Neassán, making him a deacon and founded a church for him in Mungret.