The Origin of the name "Yankee"
Yankee is the nickname that Americans themselves awarded to the people of Connecticut, and later to all of New England. In the rest of the world that name came to apply to all Americans.
There are a quite few stories about the exact origin of this name.
Janke, Eankke, Yankie
The nicest one comes from the Dutch , as early as 1650. They will tell you that the first name "John " was extremely common with the first English settlers of Connecticut. Now in Dutch, this name translates as "Jan", and its diminutive is "Janneke " or little John. In Dutch dialect, this is pronounced as "Janke ".
Another theory, far less friendly, states that Yankee comes from the Cherokee word "eankke ", which means "cowardly".
Still another plausible explanation comes from the Scottish dictionary. The Scots where often overwhelmed by the smart traders from New England, and so they may have used the Gallic word "yankie ", which means cunning woman...
However it may be, even earlier than 1775, the British mockingly described every American colonist as a "Yankee".
During the American Revolution the Americans proudly adopted this nickname as their own, and the famous "Yankee Doodle" became a patriotic song.
During the Civil War (1861 - 1865), the south always referred to the north as Yankees.
After World War I (1914-1918), this name was spread over Europe and the rest of the world by Parisian newspapers.