Costello — The Norman Who Became Gaelic

Costello descends from the Norman de Angulo family, who arrived in Connacht in the thirteenth century and, within a generation or two, adopted the Gaelic name Mac Oisdealbhaigh — ‘son of Oisdealbhach’ — after an early ancestor. Their territory in County Mayo is still known today as the barony of Costello.

A Norman name that didn't just soften into Irish life — it vanished into it so completely that a barony on the map is the only trace the old name Angulo left behind.

Irish form: Mac Oisdealbhaigh