Rev. Alban Butler (171173). Volume I: January. The Lives of the Saints. 1866.
St. Nennius, or Nennidhius, Abbot in Ireland
DESPISING the vanities of the world, though of the race of the monarchs of Ireland, from his youth made the science of the cross of Christ the sole object of his ambition; and to engrave in his heart the lessons which our divine Redeemer taught by that adorable mystery, was the centre of all his desires. Having passed many years, first in the school of St. Fiechus, archbishop of Leinster, and afterwards in the celebrated monastery of Clonard, in the province of Meath, under its holy founder St. Finian, he retired into the isle of Inis-muighe-samb, in the lake of Erne, in the province of Ulster. Here, in process of time, he became the director of many souls in the paths of christian perfection, founded a great monastery, and, on account of his eminent sanctity, and the number of illustrious disciples whom he left behind him, is called one of the twelve apostles of Ireland. He flourished in the sixth century, and has been honoured in Ireland among the saints. F. Colgan was not able to meet with any acts of his life, though he is mentioned in the lives of several other Irish saints. A church in the isle of the lake, formed by the river Erne, is dedicated to God under his invocation.