Trivia: There are two spellings:
1. Flack is a public relations fibber.
2. Flak is a German abbreviation for flieger abwehr kanone = antiaircraft gun or antiaircraft fire (from its association with the weapon). Its current usage is a slang term for people who oppose another person's point of view. Example: “When you're catching a lot of media flak, you've hit their soft spot.”