The name Britain descends from the Latin name for Britain, Britannia or Brittānia, the land of the Britons.
Britannia was used by the Romans from the 1st century BC for the British Isles taken together.
The term Great Britain was first used officially in 1474, in the instrument drawing up the proposal for a marriage between Cecily the daughter of Edward IV of England, and James the son of James III of Scotland, which described it as "this Nobill Isle, callit Gret Britanee". It was used again in 1604, when King James VI and I styled himself "King of Great Brittaine, France and Ireland".