The name Britain is derived from the Latin name Britannia (earlier Brittannia), via Old French Bretaigne (whence also Modern French Bretagne) and Middle English Bretayne, Breteyne. The French form replaced Old English Breoton, Breoten, Bryten, Breten (also Breoton-lond, Breten-lond).
Brittannia or Brittānia was the name used by the Romans from the 1st century BC. Following the Roman conquest of AD 43, it came to be used for the Roman province, which was restricted to the island of Great Britain south of Hadrian's wall. Because of this, Brittannia was increasingly used for Great Britain in particular, which had formerly been known as Albion.
The form with single -t-, Britannia, is secondary, but can be traced to the Roman period.[1]
Latin Britannia is derived from the travel writings of the ancient Greek Pytheas around 320 BC, which described various islands in the North Atlantic as far North as Thule (possibly Iceland, Faroe, or the Shetland Islands).[2] Pytheas described Thule as the northernmost part of Πρεττανική (Prettanike) or Βρεττανίαι (Brettaniai), his term for the entire group of islands in the far north-west.[3][4][5] Diodorus in the 1st century BC introduced the form Πρεττανια Prettania, and Strabo (1.4.2) has Βρεττανία Brettania. Marcian of Heraclea in his Periplus maris exteri describes αἱ Πρεττανικαὶ νῆσοι "the Prettanic Isles". Stephanus of Byzantium glosses Ἀλβίων Albion as νῆσος Πρεττανική, Μαρκιανὸς ἐν περίπλῳ αὐτῆς. τὸ ἐθνικὸν Ἀλβιώνιος ("the Pretannic island, according to Marcian in his periplus; the Albionian people" Ethnica 69.16).
The inhabitants of the islands were called the Πρεττανοι (Priteni or Pretani).[4] The shift from the "P" of Pretannia to the "B" of Britannia by the Romans occurred during the time of Julius Caesar.[4] By the 1st century BC Britannia was being used to refer to Great Britain specifically, due to the Roman conquest and the subsequent establishment of the Roman province of Britannia, which eventually came to encompass the part of the island south of Caledonia (roughly, Scotland).
Priteni is the source of the Welsh language term Prydain, Britain, which has the same source as the Goidelic term Cruithne used to refer to the early Brythonic-speaking inhabitants of Ireland and the north of Scotland.[5] The latter were later called Picts or Caledonians by the Romans.
The name Britons for the inhabitants of Great Britain is a loan from Old French bretun, the term for the people and language of Brittany, ultimately via Latin from the Βρίττωνες of Procopius, introduced in Middle English as brutons in the late 13th century.[6] Brittia appears as a name for Great Britain in Procopius, reportedly used by the 6th-century population of what is now the Netherlands.
The Latin term (Bede has Brittania) is loaned into Old English by Alfred the Great as bryttania. The 9th-century Historia Brittonum gives an origin myth involving Brutus of Troy.