O'Shaughnessy is an Irish surname primarily found in County Galway and County Limerick. It is an Anglicized form of Ó Seachnasaigh, meaning "descendant of Seachnasach." The given name Seachnasach possibly means "elusive" in Irish.Etymology and HistoryThe Ó Seachnasaigh family, collectively known as Uí Sheachnasaigh, belonged to the clan Cinél nAedha na hEchtghe (modern Irish, Cinéal nAedha na hEchtghe), meaning "kindred of Aedh of the Slieve Aughty." Their name derives from Seachnasach mac Donnchadh, a 10th-century member of the Uí Fiachrach Aidhne, of which the Ó Seachnasaigh were the senior clan. 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.TerritoryUp until the late 17th century, the Ó Seachnasaighs held the sub-district of Uí Fiachrach Aidhne known as Cenél Áeda na hEchtge, which roughly consisted of the civil parishes of Beagh, Kilmacduagh, and Kiltartan, as well as parts of other parishes.VariantsVariants of the surname include Shaughnessy and the original Gaelic form Ó Seachnasaigh.Meaning: Descendant of Seachnasach (possibly "the elusive one")Origin: Irish (Gaelic)Type: SurnameUsage Regions: Ireland (Galway, Limerick)