Farrelly is an anglicised form of Ó Faircheallaigh, a family name of the Irish nobility from County Cavan.

While the Irish title for a saint's heir can be coarb or erenagh, the Annals of the Kingdom of Ireland provide an authoritative translation in a note for the year 1025: Dubhinsi Ua Faircheallaigh, herenagh of Druim-leathan [...] died.

"[6] The Life of Máedóc of Ferns states: "Once when Máedóc was at Ferns at the end of his time, the angel of the Lord revealed to him that the term of his days and the end of his life was now approaching and drawing nigh, and bade him go to the place of his resurrection, and to the site of his burial, and to leave his churches and noble annoits, and his chosen sanctuaries, to their native gentry and to their proper heirs after him.

He left Ferns and its lands under the authority of Cele and Aedan, and with their race and descendants, together with the perpetual obligation of levying and collecting the tribute dues of Leinster, and of dividing them impartially among his churches and coarbs, as we said above.

After Faircheallaigh died, the protection of the church was entrusted to the welcoming countenance which never refused a company, to the noble man, to Maelchiaráin.