What is "o'shaughnessy"

Ó Seachnasaigh, O'Shaughnessy, collectively Uí Sheachnasaigh, clan name Cinél nAedha na hEchtghe, is a family surname of Irish origin. The name is found primarily in County Galway and County Limerick. Their name derives from Seachnasach mac Donnchadh, a 10th-century member of the Uí Fiachrach Aidhne, which the Ó Seachnasaigh were the senior clan of. The town of Gort, Ireland, was the main residence of the family since at least the time of their ancestor, King Guaire Aidne mac Colmáin.