Yankee

[frank]

<<<Most probably, however, it comes from Dutch nickname for Jan "John"—Janke, where Dutch 'j' = [y].<<<

This poses a problem, since in most Dutch (dialects and older forms) the diminutive after a dental is -tje > Jantje, or an extra vowel is inserted > Janneke.
In Fryslân, Janke is common, though (m/f).
In Germany, it's a fairly common family name.

In the booklet Total Dutch. Meer dan duizend woorden en uitdrukkingen met Dutch, vertaald, verklaard en toegelicht (More than a 1000 words and expressions with Dutch translated and explained), the authors give the following comments:
- The word is derived from Janke (diminutive of Jan];
- Yankee is derived from the two common names Jan and Kees. Quote: "This nonsense is often told in the Netherlands";
- Originally, it was yankey and it would refer to the name of a ship or a captain;
- Yankee is the result of the wrong pronunciation by indians of the word anglais;
- from eankke, salve, taken from an indian language;
- from Yaquis, the name of an indian tribe;
- from Scottish yankie, meaning smart;

[All these explanations are dismissed. And i'm sorry, but the authors are very concise in their explanations.]

The explanation that gets most credits is...
Jan Kees, but Kees meaning "cheese". Seems that already in the 17th century the Dutch were called "Jan Kaas", John the Cheese. Inquite a few dialects kaas is pronounced as kees. (in Belgium, the Dutch are still often referred to as kaaskop, or keeskop, lit. cheesehead).
Since "Jan Kees" is perceived as a plural in English, it became Jankee > English orthography Yankee.

Frank

[Slava]

Re-posted by the author here: http://www.alphadictionary.com/bb/viewtopic.php?t=452

There's more commentary there, too, so check it out.