He was educated under St. Finian at Clonard,[5] where his fellow students included Ciarán of Clonmacnoise, St. Molaise of Devenish and St. Aidan of Ferns.

[3] Ninnidh likely journeyed up and down the Southern portion of Lower Lough Erne in a hollowed-out boat, coming ashore and making his way inland to meet people and spread the gospel.

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.

St. Ninnidh's well is situated at Knockninny Quay on the shores of Upper Lough Erne and is reputed to have curative properties for eye ailments.

In William Henry's Upper Lough Erne in 1739 the well was described as a chief curiosity, "being a plentiful foundation of pure water, having a clearance and coolness scarce to be met with.

It was at that time a popular spot for boatspeople to retire to for their entertainments for which and around it are arranged benches of sod and over it a shade of aquatic trees".