O'Neill, Flaithbheartach (DNB00)
O'NEILL, FLAITHBHEARTACH (d. 1036), king of Ailech, son of Muircheanach (d. 943) [q. v.], and grandson of Niall (810?–919) [q. v.], is sometimes called Flaithbheartach an trostain, i.e. of the pilgrim's staff—a name given to him because he went on a pilgrimage to Rome. He first appears in the chronicles in 1004, when he ravaged the district of Lethchathail, now Locale, co. Down, and then part of the kingdom of Lesser Ulster or Ulidia. He slew the king of Lethchathail, and in a second battle overthrew the Ulidians and killed the heir of the chief of the Ui Eathach, their allies. In 1005 he plundered Conaille Murtheimhne, a level district of Louth, but was attacked and defeated with great loss by Maelseachlainn II [q. v.], king of Ireland; but next year he again invaded Ulidia, and slew another lord of Lethchathail, Cuuladh Mac Aenghasa, taking home seven hostages. In 1008 he plundered the rich idain called Magh Breagh in the south of Sleath, and in 1010 in alliance with Munstermen under Murchadh, son of Brian (926-1014) [q. v.], king of Ireland, and with some of the southern O'Neills from Meath, he attacked Cinel Luighdheach, now the barony of Kilmacrenan, co. Donegal, then the patrimony of the O'Donnells, and carried off three hundred cows. Later in the year he demolished Dun Eathach, a fortress in Ulidia. lie invaded the Cinel Conaill as far as Moy, co. Donegal, in 1012, and later marched right through it to Drumcliff, co. Sligo. In his absence, Maelseachlainn invaded Tyrone, but retired, and Flaithbheartach attacked the Ards, co. Down, and again obtained a great spoil from the Ulidians. In 1013 he attacked Meath by way of Maighin attaed, a place not hitherto identified, but which is clearly Moynalty, CO. Meath, since the chronicle adds, 'i ttaobh Ceanannsa' (near Kells), a phrase which, by a misprint in O'Donovan's translation of the 'Annals of the Four Masters,' is rendered 'by the son of Cenanus.' The pass by which the Ulstermen came down may still be traced in the hills on the right bank of the river Borora, which here divides Cavan from Meath. He slew Muireadhach Ua Duibheoin, chief of Ui Micuaisbreagh in Meath, in 1017, and in 1018 was at war with Maelseachlainn, the king of Ireland. Next Year he again ravaged O'Donnell's country. He was defeated by the people of Magh Breagh in 1025, but again invaded Meath in 1025. In 1030 he went on a pilgrimage to Rome, and came back in 1031. It was a year of plenty, and he was able to lead a force into Inishowen. In 1036 he died, iar ndeighbheathaidh agus iar bpennain' ('after a good life and penance'), says the chronicle. He had two sons: Domhnall, who died in 1027; and Muireadhach, who was slain by the Ui Labhradha, a sept of the Ulidians, in 1039.
[Annala Riogbuchta Eireann, ed. O'Donovan, vol. ii.; Annals of Ulster (Rolls Ser.), ed. Hennessy and MacCarthy; Annals of Loch Cé (Rolls Ser.), ed. Hennessy.]