The Greco-Egyptian scientist Ptolemy referred to the larger island as great Britain (μεγάλη Βρεττανία megale Brettania) and to Ireland as little Britain (μικρὰ Βρεττανία mikra Brettania) in his work Almagest (147–148 AD).
In his later work, Geography (c. 150 AD), he gave the islands the names Alwion, Iwernia, and Mona (the Isle of Man), suggesting these may have been the names of the individual islands not known to him at the time of writing Almagest.
The name Albion appears to have fallen out of use sometime after the Roman conquest of Britain, after which Britain became the more commonplace name for the island.

After the Anglo-Saxon period, Britain was used as a historical term only.

Geoffrey of Monmouth in his pseudohistorical Historia Regum Britanniae (c. 1136) refers to the island as Britannia major ("Greater Britain"), to distinguish it from Britannia minor ("Lesser Britain"), the continental region which approximates to modern Brittany, which had been settled in the fifth and sixth centuries by migrants from Britain.
The term Great Britain was first used officially in 1474, in the instrument drawing up the proposal for a marriage between Cecily, daughter of Edward IV of England, and James, son of James III of Scotland, which described it as "this Nobill Isle, callit Gret Britanee".
It was used again in 1604, when James VI and I styled himself "King of Great Brittaine, France and Ireland".
The Greco-Egyptian scientist Ptolemy referred to the larger island as great Britain (μεγάλη Βρεττανία megale Brettania) and to Ireland as little Britain (μικρὰ Βρεττανία mikra Brettania) in his work Almagest (147–148 AD). In his later work, Geography (c. 150 AD), he gave the islands the names Alwion, Iwernia, and Mona (the Isle of Man), suggesting these may have been the names of the individual islands not known to him at the time of writing Almagest. The name Albion appears to have fallen out of use sometime after the Roman conquest of Britain, after which Britain became the more commonplace name for the island.
After the Anglo-Saxon period, Britain was used as a historical term only.
Geoffrey of Monmouth in his pseudohistorical Historia Regum Britanniae (c. 1136) refers to the island as Britannia major ("Greater Britain"), to distinguish it from Britannia minor ("Lesser Britain"), the continental region which approximates to modern Brittany, which had been settled in the fifth and sixth centuries by migrants from Britain. The term Great Britain was first used officially in 1474, in the instrument drawing up the proposal for a marriage between Cecily, daughter of Edward IV of England, and James, son of James III of Scotland, which described it as "this Nobill Isle, callit Gret Britanee". It was used again in 1604, when James VI and I styled himself "King of Great Brittaine, France and Ireland".
Great Britain