Ó Seasnáin
Ó SEASNÁIN—I—O Sesnane, O Shesnan, Shasnan, (Sexton); 'descendant of Seasnán' or 'Seascnán'; the name of a Dalcassian family in Thomond. At the end of the 16th century it was found in different parts of Munster and also in Longford, Cavan and Monaghan. The anglicised form 'Sexten' appears as early as the year 1533 in the city of Limerick, where a respectable branch of the family had settled.
Alphabetical Index to Irish Surnames