The name Britain originates from the Common Brittonic term *Pritanī and is one of the oldest known names for Great Britain, an island off the north-western coast of continental Europe. The terms Briton and British, similarly derived, refer to some or all of its inhabitants and, to varying extents, those of the smaller islands in the vicinity. "British Isles" is the only ancient name for these islands to survive in general usage.
Etymology
"Britain" comes from , via Old French and Middle English , possibly influenced by Old English , probably also from Latin Brittania, ultimately an adaptation of the Common Brittonic name for the island, *Pritanī.
The earliest written reference to the British Isles derives from the works of the Greek explorer Pytheas of Massalia; later Greek writers such as Diodorus of Sicily and Strabo who quote Pytheas' use of variants such as (), "The Britannic [land, island]", and , "Britannic islands", with being a Celtic word that might mean "the painted ones" or "the tattooed folk", referring to body decoration (see below).
The modern Welsh name for the island is . This may demonstrate that the original Common Brittonic form had initial P- not B- (which would give **Brydain) and -t- not -tt- (else **Prythain). This may be explained as containing a stem *prit- (Welsh , Old Irish ; < Proto-Celtic ), meaning "shape, form", combined with an adjectival suffix. This leaves us with *Pritanī.
History
Written record
The first known written use of the word was an ancient Greek transliteration of the original P-Celtic term. It is believed to have appeared within a periplus written in about 325 BC by the geographer and explorer Pytheas of Massalia, but no copies of this work survive. The earliest existing records of the word are quotations of the periplus by later authors, such as those within Diodorus of Sicily's history (c. 60 BC to 30 BC), Strabo's Geographica (c. 7 BC to AD 19) and Pliny's Natural History (AD 77). According to Strabo, Pytheas referred to Britain as Bretannikē, which is treated a feminine noun. Although technically an adjective (the Britannic or British) it may have been a case of noun ellipsis, a common mechanism in ancient Greek. This term along with other relevant ones, subsequently appeared inter alia in the following works: Pliny referred to the main island as Britannia, with Britanniae describing the island group. Catullus also used the plural Britanniae in his Carmina. Avienius used insula Albionum in his Ora Maritima. Orosius used the plural Britanniae to refer to the islands and Britanni to refer to the people thereof. Diodorus referred to Great Britain as Prettanikē nēsos and its inhabitants as Prettanoi. Ptolemy, in his Almagest, used Brettania and Brettanikai nēsoi to refer to the island group and the terms megale Brettania (Great Britain) and mikra Brettania (little Britain) for the islands of Great Britain and Ireland, respectively. However, in his Geography, he referred to both Alwion (Great Britain) and Iwernia (Ireland) as a nēsos Bretanikē, or British island. Marcian of Heraclea, in his Periplus maris exteri, described the island group as (the Prettanic Isles). Stephanus of Byzantium used the term Ἀλβίων (Albion) to refer to the island, and Ἀλβιώνιοι (Albionioi) to refer to its people. Pseudo-Aristotle used nēsoi Brettanikai, Albion and Ierne to refer to the island group, Great Britain, and Ireland, respectively. Procopius, in the 6th century AD, used the terms Brittia and Brettania though he considered them to be different islands, the former being located between the latter and Thule. Moreover, according to him on Brittia lived three different nations, the homonymous Brittones (Britons), the Angiloi (English) and the Phrissones (Frisians).
As seen above, the original spelling of the term is disputed. Ancient manuscripts alternated between the use of the P- and the B-, and many linguists believe Pytheas's original manuscript used P- (Prettania) rather than B-. Although B- is more common in these manuscripts, many modern authors quote the Greek or Latin with a P- and attribute the B- to changes by the Romans in the time of Julius Caesar; the relevant, attested sometimes later, change of the spelling of the word(s) in Greek, as is also sometimes done in modern Greek, from being written with a double tau to being written with a double nu, is likewise also explained by Roman influence, from the aforementioned change in the spelling in Latin. For example, linguist Karl Schmidt states that the "name of the island was originally transmitted as Πρεττανία (with Π instead of Β) ... as is confirmed by its etymology".