Shaughnessy, ó Seachnasaigh A Gaelic surname meaning descendant of Seachnasach. A sept of the Ui Fiachrach Aidhne. On the decline of the O’Cahill in the thirteenth century, they became chiefs of Cinel Aodha (Kinelea, the district lying around Gort in Galway). In 1890 the surname was principally found in Galway (50%), and the estimated number of bearers was 1,840. In the United States Shaugnasessy is the 7,872nd most numerous surname with an estimated 2,750 bearers, and O’Shaughnessy is the 9,923rd most numerous surname with an estimated 2,750 bearers.
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