Britn.

Brit (n.)U.S. colloquial shortening of Britisher or Briton, 1901, formerly (in common with Britisher) highly offensive to Englishmen traveling in the States, who regarded it as yet another instance of the "odious vulgarism" of the Americans, but Bret and Bryt were common Old English words for the (Celtic) Britons and survived until c. 1300. In Old French, Bret as an adjective meant "British, Breton; cunning, crafty; simple-minded, stupid."