1707,The Acts of Union, passed by the English and Scottish Parliaments in 1707, led to the creation of the United Kingdom of Great Britain ,ununited kingdom of not so great britain now. we must also marvel at the idea of calling a country "great" which i am sure we were,even if not now!
Now you're doing it!
"Great" Britain means "Bigger" Britain not "better" Britain.
We're bigger than Brittany (the other "Britain")
Here's a video explanation from a genuinely great, british comedian
http://www.youtube.com/watch?v=SdVnEbHZjzo
And while I was finding that here's another misuse of language people should be aware of
http://www.youtube.com/watch?v=om7O0MFkmpw