Original: The name "Great Britain" (then spelled "Great Brittaine") was first used by James VI/I in October 1604, who indicated that henceforth he and his successors would be viewed as Kings of Great Britain, not Kings of England and Scotland.
Simplified: The name "Great Britain" (then spelt "Great Brittaine") was first used by James VI/I in October 1604, who indicated that henceforth he and his successors would be viewed as Kings of Great Britain, not Kings of England and Scotland.