Clan: Costelloe of Ballaghaderreen, Frenchpark, Fairymount and Loughglynn
Other branches of the clan: Costello, Cassells, Costelloe, MacCostelloe, MacOisdealbhaigh, Casserly, Mac Casarlaigh, Costley, Cushely, Cuskley, Costely, Mac Giolla Choiscle.
The Costelloes are descended from an Anglo-Norman family named de Angulo that came to Ireland at the end of the Twelfth century. These Norman knights went to live in the Connacht Province.
In 1193, they appear in The Annals of the Four Masters where they were called sons of Oistealb. He was a son of Gilbert de Nangle, and his family was called Mac Oisdealbhaigh. This name became MacCostello. The Costello name still occurs in the Connacht Province, in Galway, Clare and Mayo. In Mayo, it is spelt as Costello and with an “e” in Galway and Clare.
They are part of the ancestral home of the Costelloes and form a stage of the Beara-Breifne Greenway which is based on the historic march of O’Sullivan Beara in 1603.