quisling

[eberntson]

quisling (noun) a traitor who collaborates with an enemy force occupying their country.

Origin: Second World War: from the name of Major Vidkun Quisling (1887–1945), the Norwegian army officer and diplomat who ruled Norway on behalf of the German occupying forces (1940-45)

(src: OED)

[MTC]

Let's not overlook Philippe Pétain or Marshal Pétain who headed the collaborationist French government in Vichy during WW II. He deserves at least as much "credit" as Quisling. It would be fascinating to hear an expert like Dr. Beard explain why Quisling's name became synonymous with treachery, while Pétain's name fell into obscurity, except perhaps in France.
When one flower whithers, another blooms.

[Slava]

Synonymous? And here I thought it was eponymous.