UaCerbaill. After becoming king of Ulaid, Eochaid
too revolted, provoking the high king. Eochaid was
duly banished, allowing Muirchertach to give the king-
ship to Donnsléibe Ua Duinnsléibe. Undeterred,
Eochaid attempted to take back his kingship, but was
expelled by the Ulaid and captured by Ua Cerbaill.
The latter brought a repentant Eochaid before
Muirchertach at Armagh and asked for him to be
restored. The high king agreed, but charged Eochaid
a heavy penalty in hostages, jewels, and land, granting
the land to Ua Cerbaill and the church. In 1166,
Muirchertach’s world and high kingship unwound
amid serious rebellions in Armagh, Derry, and parts of
Tír nEógain. After killing one of the probable perpet-
uators, Áed Ua Máelfabaill, lord of Carraig Brachaide
in northwest Inishowen, he then spent Easter with
Eochaid. But he became suspicious of Eochaid and
arrested him after a feast. Although Eochaid was under
the protection of Archbishop Gilla mac Liag and Ua
Cerbaill, Muirchertach ordered him and three promi-
nent nobles of the Dál Riata blinded. The punishment
meted out to Eochaid cost Mac Lochlainn dear, as his
allies deserted him. An outraged Ua Cerbaill revolted
and appealed to Ruaidrí Ua Conchobair, recognizing
him as high king at Drogheda. At the head of large
army, Ua Ruairc and Ua Cerbaill invaded Tír nEógain
to hunt Muirchertach down. They found him with a
small force near the woods of Uí Echach in the Fews
of Armagh, defying them. During the ensuing conflict,
he was beheaded by a soldier of Airgialla. He was
buried at Armagh (a snub to Bishop Ua Brolcháin of
Derry) and was survived by five sons.
EMMETO’BYRNE
References and Further Reading
Hennessy, W., and B. Mac Carthy. ed. The Annals of Ulster.
4vols. Dublin: 1887–1901.
———.The Annals of Loch Cé. 2 vols. London, 1871.
O’Donovan, John, ed. The Annals of the Four Masters. 7 vols.
Dublin: 1851.
Ó hInnse, Séamus, ed. Miscellaneous Irish Annals. Dublin: Irish
Manuscript Commission, 1947.
Mac Airt, Seán. The Annals of Inisfallen. Dublin: Dublin Insti-
tute for Advanced Studies, 1951.
Murphy, Denis. The Annals of Clonmacnoise. Dublin: Royal
Irish Academy, 1896.
Stokes, Whitley, ed. “The Annals of Tigernach.” Rev. Celt 16–18
(1895–1897).
Hogan, James. “The Irish Law of Kingship, with Special Ref-
erence to Ailech and Cenél nEógain.” Proceedings of the
Royal Irish Academy, vol. 40, sec. C (1932): 186–254.
Ua Ceallaigh, Séamus. Gleanings from Ulster History. Cork:
Cork University Press, 1951. Reprint, Draperstown:
Ballinascreen Historical Society, 1994.
Simms, Katharine. “Tír nEógain North of the Mountain.” In
Derry & Londonderry: History and Society, edited by
Gerard O’Brien, pp. 149–174. Irish County History Series.
Dublin: Geography Publications, 1999.
Byrne, F. J. Irish Kings and High-Kings. London: B. T. Batsford,- Reprint, Four Courts Press: Dublin, 2001.
Ó Corráin, Donncha. Ireland before the Normans. Dublin, 1972.
See alsoMac Murchada, Diarmait; Ua Conchobair,
Ruaidrí; Ua Conchobair; Tairrdelbach
MAC MAHON
The Mac Mahon (Mac Mathgamna) family were
Gaelic lords of Airgialla (Oriel), approximating to
what is now County. Monaghan, during the late medi-
eval period, on the marchlands of Gaelic Ulster and
the northern Pale. They are first mentioned in the
annals in 1181, and were related to the previous Ua
Cerbaill ruling dynasty of Airgialla who surrendered
the lordship to the Mac Mahons in the late twelfth
century. The Mac Mahons were a border people, who
came alternately under pressure from Ua Néill, lord of
Tír nEógain, and the Anglo-Irish of Louth. Throughout
the entire medieval period the Mac Mahon lordship
was also a relatively poor region. There were no impor-
tant religious houses or Mac Mahon castles, although
during the fifteenth century the Mac Mahon lords did
become noted patrons of bardic poets.
The first powerful Mac Mahon ruler was Niall, who
ruled Airgialla in the late twelfth and early thirteenth
centuries. Niall employed mercenary bandits and
moved the Mac Mahons from Farney into Cremorne.
He fought both English and Irish enemies, being an
ally of John de Courcy. His most notable exploit was
the killing of Éicnecán Ua Domnaill, lord of Tír
Conaill in 1207, who was killed while on a raid into
Fermanagh. The Mac Mahons came under severe pres-
sure from the English of Louth in the 1250s and 1260s,
which greatly weakened the family. They then came
under the overlordship of the earls of Ulster and the
de Verdons of Louth, who imposed claims for military
service on them. As the fourteenth century progressed,
the dynasty became more powerful, and by the end of
that century various branches of the Mac Mahon fam-
ily ruled the territories of Farney, Cremorne, Dartry,
and Monaghan, with the Mac Kenna family of Truagh
under the overlordship of the ruling Mac Mahon. The
mid-fourteenth-century lord, Brian Mór, was the most
powerful ruler of Airgialla. In 1346, he won a great
victory over the English of Louth when he killed over
300 English soldiers. In 1365, Brian “assumed the
lordship of Airgialla,” but became embroiled in a war
with Ua Néill of Tír nEógain for drowning Somhairle
MacDomnaill, Ua Néill’s galloglass constable. Brian
Mór’s chief fortress was at Rath-Tulach in the barony
of Monaghan. He was slain in 1372 by one of his own
bodyguards. Brian Mór levied black rents on the Eng-
lish of Louth, which included tributes of fine clothes,
silver, and malt, and was referred to as “undisputedMAC LOCHLAINN, MUIRCHERTACH (C. 1110–1166)