" You have defiled my honor!” Stilgar cried. “This is neutral—” “Shut up!” Idaho glared at the shocked Naib. “You wear a collar, Stilgar! ” It was one of the three most deadly insults which could be directed at a Fremen. Stilgar’s face went pale. “You are a servant,” Idaho said. “You’ve sold Fremen for their water.” This was the second most deadly insult, the one which had destroyed the original Jacurutu. "

― Frank Herbert , Children of Dune (Dune, #3)