The Kingdom of Breifne or Bréifne (anglicized Breffny, Brefnie or Brenny) was the traditional territory for an early Irish tribal group known as the Uí Briúin Bréifne. The Bréifne territory included the modern Irish counties of Leitrim and Cavan, along with parts of County Sligo (an area roughly equivalent to the modern Roman Catholic Diocese of Kilmore).
The standard meaning of Breifne until recently was that it means “hilly” in Irish, a description which describes the topography of this part of Ireland. However recent advances in language studies indicate that the name is derived from the pre-Celtic substrate language spoken in Ireland before the arrival of the Celts and means “Ring” or “Loop”. Breifne would therefore have one of the oldest placenames in Ireland, dating from prior to 500 BC.
In ancient times the area that became to be known as Bréifne was said to be occupied by the Erdini, called in Irish ‘Ernaigh’, who possessed the entire country bordering Lough Erne.
At the beginning of the Christian era in Ireland (circa 5th–6th century) tribal groupings believed to be in or near Breifne included the Glasraighe, Masraige, Dartraige, Armhaighe, Gallraighe, the Fir Manach, and the Gailenga.
Around the 6th century a people known as the Conmaicne Rein are thought to have moved north from around the present Dunmore in County Galway and settled in Magh Rein (the area around Fenagh). From here they peopled what is now South Leitrim, which became known as Magh Rein, and its inhabitants as the Conmaicne Magh Rein. They consisted of different family groupings – Muintir Eolais, Muintir Cearbhallain (O Mulvey), and Cinel Luachain, among others.
About the 8th century, the area since known as Breifne was conquered and settled by the Uí Briúin who were a branch of the royal family of Connacht. The Uí Briúin established themselves first in modern county Leitrim and then into what is now County Cavan. It can be argued that there is no contemporary evidence to support these speculations. It is a great pity that this entire entry does not display any critique of historical sources.
By the 9th century the O’Ruaircs had established themselves as kings of Breifne.
In the 10th and 11th centuries the O’Ruairc kings of Breifne fought some battles for the title of king of Connacht, four different kings of Breifne gaining the title.
During the 12th century the reign of Tighearnán Ua Ruairc, the kingdom of Breifne was said to comprise most of the modern counties of Leitrim and Cavan, and parts of Longford, Meath, Fermanagh and Sligo.
In the 16th century Breifne O’Rourke eventually became Co. Leitrim and Breifne O’Reilly became Co. Cavan.
