Muiredach was an ealdorman

Ealdorman

An ealdorman is the term used for a high-ranking royal official and prior magistrate of an Anglo-Saxon shire or group of shires from about the ninth century to the time of King Cnut...

  in northern England

Northern England

Northern England, also known as the North of England, the North or the North Country, is a cultural region of England. It is not an official government region, but rather an informal amalgamation of counties. The southern extent of the region is roughly the River Trent, while the North is bordered...

 in the reign of Edgar the Peaceable. He is recorded in subscriptions to two royal charter

Charter

A charter is the grant of authority or rights, stating that the granter formally recognizes the prerogative of the recipient to exercise the rights specified...

s.

The first, Sawyer 679, is a grant by King Edgar to Oscytel, Archbishop of York of 10 hide

Hide (unit)

The hide was originally an amount of land sufficient to support a household, but later in Anglo-Saxon England became a unit used in assessing land for liability to "geld", or land tax. The geld would be collected at a stated rate per hide...

s at Hutton in Nottinghamshire

Nottinghamshire

Nottinghamshire is a county in the East Midlands of England, bordering South Yorkshire to the north-west, Lincolnshire to the east, Leicestershire to the south, and Derbyshire to the west...

, where he is named Mirdach dux, ninth on the ealdorman list between Leod dux and Ascured dux.

His other appearance is in a newly discovered charter (found again 1983) issued by King Edgar to one Æthelferth, granting 5 hides at Ballidon

Ballidon

Ballidon is a village and civil parish in the Derbyshire Dales district of Derbyshire, England, on the edge of the Peak District National Park. According to the 2001 census it had a population of 79....

 in Derbyshire

Derbyshire

Derbyshire is a county in the East Midlands of England. A substantial portion of the Peak District National Park lies within Derbyshire. The northern part of Derbyshire overlaps with the Pennines, a famous chain of hills and mountains. The county contains within its boundary of approx...

, where he is named Myrdah dux and appears eighth (last) in the ealdorman list, above Gunner dux. His name precedes Oslac dominus ("Lord Oslac"), who is probably Oslac

Oslac of York

Oslac is regarded as the first ealdorman of York and its dependent territories. These included but may not have been limited to the southern half of Northumbria. His background is obscure because of poor source documentation...

, future ealdorman of Northumbria.

The names Mirdach and Myrdah represented the Goidelic name Muiredach, and he is thus thought to be of Gaelic

Gaels

The Gaels or Goidels are speakers of one of the Goidelic Celtic languages: Irish, Scottish Gaelic, and Manx. Goidelic speech originated in Ireland and subsequently spread to western and northern Scotland and the Isle of Man....

 or Norse-Gaelic origin. He may have been one of the Norse-Gaelic settlers resident in north-western Northumbria

Northumbria

Northumbria was a medieval kingdom of the Angles, in what is now Northern England and South-East Scotland, becoming subsequently an earldom in a united Anglo-Saxon kingdom of England. The name reflects the approximate southern limit to the kingdom's territory, the Humber Estuary.Northumbria was...

during the period.