Why was the north called the Yankee's?

During the American Civil War, the Northern troops were nicknamed 'Yankees' because of a long-existing tradition. Originally utilized to denote Americans from the New England region of the country (and even going back to Colonial times), 'Yankee' was extended to include all Northerners as a contrast to such nicknames as 'Johnny' or 'Johnny Reb' that were given to Southerners.