To the European, a Yankee is an American.
To an American, a Yankee is a New Englander.
To a New Englander, a Yankee is a Vermonter.
To a Vermonter, a Yankee is someone who eats apple pie for breakfast.
And to a Vermonter who eats apple pie for breakfast
a Yankee is someone who eats it with a knife.
As you can tell, the exact meaning of “Yankee” is unclear. Union soldiers during the American Civil War were called Yankees and it is used to describe all Americans by people from outside the United States. The etymology of the word is equally confused.
Some of of the well known theories about the word are the Daniel Webster (of dictionary fame) who first had a crack at it in 1810, claiming it derived from the Persian janghe, meaning “a warlike man” or “a swift horse.” Also by 1828, he was claiming it came from Yengeese, a Native American pronunciation of “English.” Another particularly popular theory is that it comes from Dutch, a combination of “Jan” (a popular first name) and kees (meaning “cheese”). The US Navy believes that it comes from Dutch merchants calling American sea captains yankers, meaning “wrangler.” Other theories include: a French corruption of “Anglais,” a word derived from the Scottish word “yank” (referring to a hard blow), and a British appropriation of the Cherokee word eankke, meaning “slave” or “coward.”
While none of these theories can be proven, there is evidence that it may ultimately have a Native American origin. The Lenni-Lenape referred to the English as Yankwis, though more often in the derivative Yankwako, or “English snake.” Other sources say that the Lenni-Lenape word referred to people from New England specifically, while the English proper were referred to as Saggenash and Virginians were just ominously called “long knives.”