Hugh the lazy assed youth got his nickname they say, when Mac Lochlainn King of Tyrone entered the house of his foster father, and Hugh refused to stand and acknowledge him, as he believed the rightful King of Tyrone was an O'Neill, Hugh's foster father tried to mask this by telling Mac Lochlainn he was a lazy assed youth.
Aedh an Macaemh Toinleasg or in English Hugh O'Neill was challenging Niall Mac Looghlin for the kingship of Tyrone, the Cinel Eoghain were divided.
At this juncture Rory O'Conor, who had gained the sovereignty after Murkertac's defeat, came a hosting into the territory, when, according to the Annals of Ulster: The Cinel Eoghain collected a fighting force around Niall Mac Loughlin to deliver a camp attack upon Rory's men which failed. Rory then proceeded to pillage and burn Tír Eoghain.
Hugh and Niall delivered their hostages; and thus was Rory the acknowledged King of all Ireland.
It was agreed that Cinel Eoghain should be divided between the two, Niall taking that portion of territory north of the mountain of Callain, now Slieve Gallion, in the south-east of Co Derry, the rest falling to Hugh, that is roughly speaking, the present Co Tyrone, with two parts of the adjoining counties.
This agreement does not appear to have worked smoothly, as in 1169, it is recorded in the annals of Ulster, that Conor, brother of Niall, assumed the Lordship, from which it would appear that Hugh and Niall resigned in his favor.
Conor fell in the next year in Armagh, in a quarrel with Hugh Mc Canna. Hugh O'Neill was installed in Conor's place, and received the submission of his neighbours.
In 1171 he appears to have dispatched a force to the assistance of Rory O' Conor, who was engaged in the siege of Dublin, where he was soon after disastrously defeated, Strongbow, at the head of 600 men, marched unobserved to where the Ulidians were encamped at finglas and took them by surprise.
Some months later Henry II. came to Ireland, and encamped in the city during the winter of 1171. Here he is said to have received, either personally or by deputy, the submission of all the Irish princes except O'Neill of Ulster, who, alone, stood out, as the Book of Howth says " The King of Ulster came not to the King. When O'Neill refused submission in 1171, Henry adopted the usual Norman policy as practised towards Wales. He made a grant of all the lands he could conquer in Ulster to one of his courtiers, John De Courcy, to hold as palatine fief; or in others words, he issued letters of marque authorizing him to rob, plunder, and steal whatever he could, and to hold it as right.
Hugh O'Neill, however, unlike his successors of the MacLoughlins sapt, could afford to despise Henry and his army - not to speak of De Courcy, by whom he was never troubled, on his own land, with a united Ulster at his back.
In 1176, Hugh's former rival, Niall was slain by the Dal Buine, his brother Malachy MacLoughlin took his place, and signalized his accession by invading Meath and taking the Castle of Slane by assault, when the garrison, under Richard Fleming, one of De Lact's followers, was put to the sword.
This created such panic among the English of those parts, that on the same day they abandoned Trim, Kells, and Derrypatrick.
The Cinel Eoghain were duly impressed, and flocked to Malachy's standard; and Hugh, deserted by most of his men, was obliged to submit to the inevitable, and resign to his more fortunate kinsman his kingship, in attempting to regain the following year Hugh was slain by Malachy and his son Ardgal.
In the four Masters this is recorded " A.D 1177, Hugh O'Neill, popularly called An Macaemh Toimleasc, who had been for some time Lord of Cinel Eoghain and heir presumptive to the throne of Ireland, was slain by Melaghlin O'Loughlin and Ardgal O'Loughlin; but Ardgal himself fell on the spot by O'Neill.
Hugh left four sons, namely, Hugh surnamed Duff ( the black ) and Niall Ruadh ( the Red ).
From Hugh Duff came the Princes of Clannaboy and from Niall the Earls of Tyrone.
Also Muircheartach, killed 1202 by the chief of MacLoughlin, and Domnall, slain by the MacLoughlin in 1239.