[Silound]

There is no official record of where the term "Yank" came to refer to Americans, but by the end of WWI it was so widely used that by WWII it had stuck. The most common theories here are either a shortening of the phrase "Yankee", or more recently a reference to the song "Yankee Doodle".

Similarly, the term "Yankee" has no clear origins, although the most common two theories involve either Cherokee origins or Dutch origins. Neither one is exactly friendly.

Most historians I have read agree that the origins of both words have probably been forgotten multiple times throughout history, and both have been re-purposed and originated again from new meaning in different time periods.