In the 10th Century the 600 year long dominance of the province of Munster by the royal Milesian Eoghanachta was challenged by the Desi Dal gCas (later O Briens). To supply some backbone to the Eoghanachta cause Duibh da Boirrean became king of Munster. He was a member of the Cineal Laoghaire (Leary’s People)
branch of the Uibh Echach or Eoghanachta Rathleinn, the other being the Cineal Aodh (Hugh’s People). Cineal Laoghaire became O Donoghues and Cineal Aodh became O Mahonys.