The term Yankee has a variety of meanings. Residents of the United States use it to refer to the baseball team, a resident of New England, or more often, a resident of the northern United States. International speakers often use it to refer to any American.
The etymology is uncertain; one suggestion is that it derives from Dutch Janke, diminutive of Jan (John), or Jan Kees, for "John Cheese," a nickname for English settlers bestowed by the Dutch in the early days of New York City. See also yankee ingenuity
Yankee has several other meanings:
Yankee Doodle, and film Yankee Doodle Dandy.