Thirteen years after the death of Tuathal, Cáthaoir [Cauheer], celebrated for his Will or Testament,[16] reigned; he was of pure Leinster blood, and the men of that province have always felicitated themselves upon having given at least this one great king to Ireland. It is from him that the great Leinster families--the O'Tooles, O'Byrnes, Mac Morroughs or Murphys, O'Conor Falys, O'Gormans, and others--descend. He was slain, A.D. 123, by Conn of the Hundred Battles.[17]
There are few kings during the three hundred years preceding and following the birth of Christ more famous than this Conn, and there is a very large body of saga collected round him and his rival Eoghan [Owen], the king of Munster who succeeded in wresting half the sovereignty from him. As the result of their conflicts that part of Ireland which lies north of the Escir Riada,[18] or, roughly speaking, that lies north of a line drawn from Dublin to Galway, has from that day to this been known as Conn's Half, and that south of the same line as Owen's Half. Owen was at last slain by him of the hundred battles at the fight of Moy Léana.
Owen, as we have seen, was never King of Ireland, but he left behind him a famous son, Oilioll[19] Olum, who was married to Sadhbh,[20] the daughter of his rival and vanquisher, Conn of the Hundred Battles, and it is to this stem that nearly all the ruling families of Munster trace themselves. From his eldest son, Owen Mór, come the Mac Carthys, O'Sullivans, O'Keefes, O'Callaghans, etc.; from his second son come the Mac Namaras and Clancys; and from his third son, Cian,[21] come the so-called tribes of the Cianachts, the O'Carrolls, O'Meaghers, O'Haras, O'Garas, Caseys, the southern O'Conors, and others. There is a considerable body of romance gathered around this Oilioll and his sons and wife, chiefly connected with the kingship of Munster.
Conn's son, Art the Lonely--so-called because he survived after the slaughter of his brothers--was slain by Mac Con, Sive's son by her first husband, and the slayer ruled in his place, being the third king of the line of the Ithians, of whom we shall read later on, who came to the throne.
He, however, was himself killed at the instigation of Cormac, son of Art, or Cormac mac Art, as he is usually designated. This Cormac is a central figure of the large cycle of stories connected with Finn and the Fenians. He was at last slain in the battle of Moy Mochruime. His advice to a prince, addressed to his son Cairbré of the Liffey, will be noticed later on, and, so far as it may be genuine, bears witness to his reputed wisdom, "as do the many other praiseworthy institutes named from him that are still to be found among the books of the Brehon Laws."[22] This Cormac it was who built the first mill in Ireland, and who made a banqueting-place of the great hall of Mi-Cuarta,[23] at Tara, which was one hundred yards long, forty-five feet high, one hundred feet broad, and which was entered by fourteen doors. The site is still to be seen, but no vestige of the building, which, like all early Irish structures, was of wood.