Seldom used to flag someone who is out to make drastic political changes. It may be used for one who's views favor radicalism or someone who wishes to be a revolutionary. Sometimes it is even used to pin someone as an anarchist.
Doon was given as the last name of a character from Hot Sleep, The Worthing Chronicle and The Worthing Saga, written by Orson Scott Card. The tale includes a man, named Abner Doon, who helps destroy man's civilized planet, Capitol, and has a new planet populated by humans with telepathic abilities, called Swipes.
Doon was an ancient Breton lai of a knight who strives to win the hand of a maiden.