In modern times the prefix O has been entirely dropped from the name Hennessy. The Irish of the name is O hAonghusa, meaning decendant of Aonghus or Aongus. The principal sept were found in County Offaly. Another sept had their lands on the borders between Counties Meath and Dublin, Many moved away to County Sligo where until recently they owned much land.
Present your clan/sept crest in a most unique and attractive way by choosing an Irish Clan/Sept Shield by Rowan Heraldic Shields!