Ó Seachnais
Ó SEACHNAIS—I—O Shaghnishe. O Shaghnes, Shaughness, Shaughnessy, &c.; a shortened form of Ó Seachnasaigh, which see; rather common in the spoken language of Connacht. I have heard it pronounced Ó Sheachnais (initial S aspirated) in West Limerick.
Alphabetical Index to Irish Surnames