A word Norwegians are not very proud of having given to the world: it derives from Vidkun Quisling (1887-1945), a Norwegian
politician who collaborated with the Nazis during World
War II. He established his name as a synonym for "traitor", someone who collaborates with the invaders of his country, especially by serving in a puppet
government.
It is, arguably, the worst and most grave insult a Norwegian can throw at another.