Today, foreigners call anybody living in the U.S. a Yankee. During the Civil War, it was specifically people in the Northeast who received that appellation, and in the early eighteenth century it referred to anybody living in Connecticut. Through all this time, it always had an underlying pejorative sense. This is all because of the Dutch influence in the New York colony, back when it was under their control, as New Netherlands: seeing the English, Puritan colonists as awfully boring and plain, they called them by a generic name: Jan Kaas, or "John Cheese". A fantastic insult for an American, no? It was meant to sound generic, and it accomplished that beautifully. Jan is a Biblical name: through Greek and then Latin Ionannes, it derives from the Hebrew name Yohanan, which probably means something like "God is gracious". Kaas, through Latin caseus, then Proto-Germanic caseus, originates from the Proto-Indo-European root kwat, meaning "to ferment". So, ultimately, Yankee means "God is gracious ferment". Yay!
Adam Aleksic has been described as the internet's sixth most famous etymologist. He loves writing about himself in the third person, he's a freshman at Harvard University, and he has disturbing interests in linguistics, vexillology, geography, board games, limericks, and law.
The Etymology Nerd