| Background: A Dalcassian sept, deriving its name and historical importance from the family of King Brian Boru. Now very numerous in other provinces as well as Munster, being the fifth most numerous name in Ireland. In some cases O'Brien has been made a synonym of O'Byrne and in others of the Norman Bryan. Primarily from Clare, Limerick, Tipperary and Waterford.
Variations: O'Brien, O'Brian, O'Bryan, Brian, Brien, Byrne.
More Info: http://heraldry.celticradio.net/search.php?id=137
Discussion of this family is welcomed.