Although none of his own writings remain, writers during the time of the Roman Empire made much reference to them.Pytheas called the islands collectively (hai Brettaniai), which has been translated as the Brittanic Isles; he also used the term Pretannike.The first inhabitants were the Britons, who came from Armenia, and first peopled Britain southward.” (“Armenia” is possibly a mistaken transcription of Armorica, an area in northwestern Gaul including modern Brittany.) The Latin name in the early Roman Empire period was Britanni or Brittanni, following the Roman conquest in AD 43.
Common Brittonic developed into the distinct Brittonic languages: Welsh, Cumbric, Cornish and Breton.The earliest known reference to the inhabitants of Britain seems to come from 4th century BC records of the voyage of Pytheas, a Greek geographer who made a voyage of exploration around the British Isles between 330 and 320 BC.During this period some Britons migrated to mainland Europe and established significant settlements in Brittany (now part of France) as well as Britonia in modern Galicia, Spain.By the 11th century, remaining Brittonic Celtic-speaking populations had split into distinct groups: the Welsh in Wales, the Cornish in Cornwall, the Bretons in Brittany, and the people of the Hen Ogledd (“Old North”) in southern Scotland and northern England.During and after the Roman era, the Britons lived throughout Britain.
Their relationship with the Picts, who lived north of the Firth of Forth, has been the subject of much discussion, though most scholars now accept that the Pictish language was related to Common Brittonic, rather than a separate Celtic language.
Pictish is now generally accepted to descend from Common Brittonic, rather than being a separate Celtic language.
Welsh and Breton survive today; Cumbric became extinct in the 12th century.
“Brittonic languages” is a more recent coinage (first attested 1923 according to the Oxford English Dictionary) intended to refer to the ancient Britons specifically.
In English, the term “Briton” originally denoted the ancient Britons and their descendants, most particularly the Welsh, who were seen as heirs to the ancient British people.
Cornish had become extinct by the 19th century but has been the subject of language revitalization since the 20th century.