The Irish surname Shannon is an anglicized form of the Gaelic name  Ó Seanáin meaning “descendant of Seanán,’ a personal name based on a pet form of seán meaning “old.” When found in County Clare, the name is an anglicized form of Mac Giolla tSeanáin meaning “son of the servant of St. Seanán.” Prior to the 14th Century, the chief of the Clare Shannon clan held territory between Bodyke and Feakle in Co. Clare. The first recorded spelling of the family name is shown to be that of O' Seannachain, a chief of the name, which was dated 1318, in the "History of Delcassian (Co. Clare) Clans."