Wikipedia
Dartraighe (older spelling: Dartraige), anglicized as Dartree, Dartry or Dartrey, was a barony in medieval Ireland which stretched north to Clones and south to the Dromore river.
The Dartraighe were an Irish tribe, also known as n-Dartraighi or Dairtre who gave their name to a territory in the western portion of what is now known as County Monaghan. The name means "calf-people". Various anglicized forms of the name were used through the years. A segment of its southern region became the Dartrey Estate, owned by Richard Dawson in the 17th century, and known as Dawson's Grove, which is now Dartrey Forest. It includes Inner Lough with its small island - probably an old crannog, which may explain the name Dartraige Coinn innsi (Dartry of the Island Chief), which occurs in the annals, perhaps to distinguish this Dartraige from another centered in Kingdom of Breifne.
Dartraighe was listed as part of the federated Kingdom of Airgíalla in the Book of Rights, and included there in a poem credited to Benén, son of Sescnén, Patrick’s cantor, though in its surviving form the composition can be dated to between 901 and 908 AD:
The king of Dartraige, a flame of valour,
is entitled to four bondsmen of great labor,
four swords hard in battle, four horses,
and four golden shields.
There are references in Irish annals in the 11th and 12th century AD to the Ui Bhaoigheallán ( O'Boylans) as chiefs of Dartraige (see below). In 1297 the sub-chiefs of the Airgíalla included the lord of Dartraighe, named as the king's brother Roalbh Mac Mathghamhna. The Ui Bhaoigheallán never recovered control of Dartraighe hereafter. It was held by the Mac Mathghamhna (MacMahons) of Airgíalla.