Yank short for Yankee. One version has it originating during the revolution when us rebels would cross over into Dutch territory in New York State to elude the Red Coats. Most Dutch in upstate were of the surname Yann/Jann or Kee. Not sure of the spelling. But the names were smashed together and we were lumped in with the Dutch.

Doodle-idiot

Dandy-spiffy dresser, thought of as putting on aires. (Also disparaging term for gays back then)