The ecclesiastical site at Glebe is associated with Saint Cummin Fada, who died around 661 or 662, and whose name turns up in connection with one of the most consequential disputes of early medieval Christianity: the question of how to calculate the date of Easter.

Cummin Fada, whose epithet Fada means "the tall" in Irish, trained at Clonfert monastery in County Galway, one of the great centres of early Irish monasticism, before establishing his own foundation at Glebe, where he served as abbot. He was a forceful advocate for the Roman method of computing Easter at a time when the Celtic church followed its own, older calculation, a disagreement that may sound technical but carried serious implications for ecclesiastical authority and the unity of the western church. What makes Cummin Fada unusual among early Irish saints is that he left documentary evidence. His Paschal epistle, known as the De controversia Paschali, survives and was edited and published in 1988 by Maura Walsh and Dáibhí Ó Cróinín for the Pontifical Institute of Medieval Studies in Toronto. For a figure associated with a modest Kerry site, that is a remarkable afterlife: an abbot whose arguments, committed to writing in the seventh century, remain readable and debated today.