The Clan/Sept History

A Clan that dates back to the Sons of Milesius. To be more precise, Heber, son of Milesius. Heber had a son that ruled after him named Eoghan Taiglech (Owen the Splendid) who in turn helped to give birth to Munster's First King - Oilloill Olum - who died in 234 A.D. King Oilloill Olum himself helped to give birth to...Cormac Cas, who is a direct ancestor of all Hannons and ruled Munster until his death in 254 A.D.
Historical records also show that "Hannon" was a sept of Siol Anmchadha in south-east Galway. By 1890, the surname was principally found in Counties Sligo, Roscommon, Limerick, Cork and Galway. Other spellings of the name are Hannan, Hanneen, Hannen, O'Hannon.