Otteran served as abbot of the Irish monastery of Tyfarnham in Meath, and founded another abbey at Latteragh in County Tipperary. Although little is known about his life, he is described as “noble and without sin.” He was later to leave Ireland with eleven others to accompany the Irish missionary priest Saint Columba on his sea journey to the Scottish island of Iona, where the latter subsequently founded the renowned Iona monastic colony. Shortly after their arrival, Otteran sensed his own death drawing near, and predicted that he would be the first monk to die on the island.

Upon hearing this, Columba, thinking ahead to his own death, replied, “Whoever makes a request at my burial-place shall not get it until he prays to you as well.” After taking leave of Otteran and giving him his blessing, Columba stepped outside, where he experienced a vision of angels battling with demons as the soul of his friend Otteran was borne to heaven. Columba learned that Otteran had in fact died just then. Iona’s cemetery grew around Otteran’s burial plot.