The Fir Domnann were an ancient Irish

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

 people located in the west and north of Connacht

Connacht

Connacht , formerly anglicised as Connaught, is one of the Provinces of Ireland situated in the west of Ireland. In Ancient Ireland, it was one of the fifths ruled by a "king of over-kings" . Following the Norman invasion of Ireland, the ancient kingdoms were shired into a number of counties for...

, in Irrus Domnann, from which Erris

Erris

Erris is a barony in northwestern County Mayo in Ireland consisting of over , much of which is mountainous blanket bog. It has extensive sea coasts along its west and north boundaries. The main towns are Belmullet and Bangor Erris. The name Erris derives from the Irish 'Iar Ros' meaning 'western...

 in County Mayo

County Mayo

County Mayo is a county in Ireland. It is located in the West Region and is also part of the province of Connacht. It is named after the village of Mayo, which is now generally known as Mayo Abbey. Mayo County Council is the local authority for the county. The population of the county is 130,552...

 now takes it's name. In Irish mythology

Irish mythology

The mythology of pre-Christian Ireland did not entirely survive the conversion to Christianity, but much of it was preserved, shorn of its religious meanings, in medieval Irish literature, which represents the most extensive and best preserved of all the branch and the Historical Cycle. There are...

 they make up one third of the Fir Bolg

Fir Bolg

In Irish mythology the Fir Bolg were one of the races that inhabited the island of Ireland prior to the arrival of the Tuatha Dé Danann.-Mythology:...

. They are probably related to the British Dumnonii

Dumnonia

Dumnonia is the Latinised name for the Brythonic kingdom in sub-Roman Britain between the late 4th and late 8th centuries, located in the farther parts of the south-west peninsula of Great Britain...

, and to the Irish Laigin

Laigin

The Laigin, modern spelling Laighin , were a population group of early Ireland who gave their name to the province of Leinster...

. They also provided the placename Inber Domnann, an old name for the Broadwater Estuary-Malahide

Malahide

Malahide is a coastal suburban town, near Dublin city, located in the administrative county of Fingal, within the traditional County Dublin, Ireland. It has a village-like centre and extensive residential areas to the south, west and northwest.-Name:...

 Bay inlet in north County Dublin

County Dublin

County Dublin is a county in Ireland. It is part of the Dublin Region and is also located in the province of Leinster. It is named after the city of Dublin which is the capital of Ireland. County Dublin was one of the first of the parts of Ireland to be shired by King John of England following the...

.

In the Táin Bó Cúailnge

Táin Bó Cúailnge

is a legendary tale from early Irish literature, often considered an epic, although it is written primarily in prose rather than verse. It tells of a war against Ulster by the Connacht queen Medb and her husband Ailill, who intend to steal the stud bull Donn Cuailnge, opposed only by the teenage...

, Ferdiad

Ferdiad

Ferdiad , son of Damán, son of Dáire, of the Fir Domnann, is a warrior of Connacht in the Ulster Cycle of Irish mythology. In the Táin Bó Cúailnge, Ferdiad finds himself on opposite sides to his best friend and foster-brother Cúchulainn, with whom he had trained in arms under the renowned warrior...

, the best friend and foster-brother of Cúchulainn

Cúchulainn

Cú Chulainn or Cúchulainn , and sometimes known in English as Cuhullin , is an Irish mythological hero who appears in the stories of the Ulster Cycle, as well as in Scottish and Manx folklore...

, by whom he was killed, was of the Fir Domnann.