Builg is the name given to an ancient people who may have lived in southern Ireland

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...

, around the modern city of Cork

Cork (city)

Cork is the second largest city in the Republic of Ireland and the island of Ireland's third most populous city. It is the principal city and administrative centre of County Cork and the largest city in the province of Munster. Cork has a population of 119,418, while the addition of the suburban...

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According to the historical scheme proposed by T. F. O'Rahilly

T. F. O'Rahilly

Thomas Francis O'Rahilly was an Irish scholar of the Celtic languages, particularly in the fields of Historical linguistics and Irish dialects. He was a member of the Royal Irish Academy.-Biography:He was born in Listowel, County Kerry, Ireland...

 the Builg are identical with or a sub-group of the Érainn or Iverni

Iverni

The Iverni were a people of early Ireland first mentioned in Ptolemy's 2nd century Geography as living in the extreme south-west of the island. He also locates a "city" called Ivernis in their territory, and observes that this settlement has the same name as the island as a whole, Ivernia...

, who arrived in Ireland ca 500 BC and are attested in Ptolemy

Ptolemy

Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

's 2nd century AD Geography. In O'Rahilly's view, they spoke a P-Celtic language known as Ivernic.

Their name may be related to both that of the Belgae

Belgae

The Belgae were a group of tribes living in northern Gaul, on the west bank of the Rhine, in the 3rd century BC, and later also in Britain, and possibly even Ireland...

 of Gaul

Gaul

Gaul was a region of Western Europe during the Iron Age and Roman era, encompassing present day France, Luxembourg and Belgium, most of Switzerland, the western part of Northern Italy, as well as the parts of the Netherlands and Germany on the left bank of the Rhine. The Gauls were the speakers of...

 and Roman Britain

Roman Britain

Roman Britain was the part of the island of Great Britain controlled by the Roman Empire from AD 43 until ca. AD 410.The Romans referred to the imperial province as Britannia, which eventually comprised all of the island of Great Britain south of the fluid frontier with Caledonia...

, and that 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:...

 of 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...

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