The word Brittany, along with its French, Breton and Gallo equivalents Bretagne, Breizh and Bertaèyn, derive from the Latin Britannia, which means "Britons' land". This word had been used by the Romans since the 1st century to refer to Great Britain, and more specifically the Roman province of Britain. This word derives from a Greek word, Πρεττανικη (Prettanike) or Βρεττανίαι (Brettaniai), used by Pytheas, an explorer from Massalia who visited the British Islands around 320 BC.
The Romans called Brittany Armorica, together with a quite indefinite region that extended along the English Channel coast from the Seine estuary to the Loire estuary, and according to several sources, maybe along the Atlantic coast to the Garonne estuary. This term probably comes from a Gallic word, aremorica, which means "close to the sea". Another name, Letauia (in English "Litavis"), was used until the 12th century. It possibly means "wide and flat" or "to expand" and it gave the Welsh name for Brittany: Llydaw.
After the fall of the Western Roman Empire, many Britons settled in western Armorica, and the region started to be called Britannia, although this name only replaced Armorica in the sixth century or perhaps by the end of the fifth. Later, authors like Geoffrey of Monmouth used the terms Britannia minor and Britannia major to distinguish Brittany from Britain.
Breton-speaking people may pronounce the word Breizh in two different ways, according to their region of origin. Breton can be divided into two main dialects: the KLT (Kerne-Leon-Tregor) and the dialect of Vannes. KLT speakers pronounce it [brɛjs] and would write it Breiz, while the Vannetais speakers pronounce it [brɛχ] and would write it Breih. The official spelling is a compromise between both variants, with a z and an h together. In 1941, efforts to unify the dialects led to the creation of the so-called Breton zh, a standard which has never been widely accepted. On its side, Gallo language has never had a widely accepted writing system and several ones coexist. For instance, the name of the region in that language can be written Bertaèyn in ELG script, or Bertègn in MOGA, and a couple of other scripts also exist.