a person hired to promote or publicize something, or harsh criticism and complaints.
From Gene Flack, a 1940s Hollywood publicist, or possibly from German Flak (anti-aircraft fire). The term evolved to mean criticism or opposition because it feels like incoming attacks.
During World War II, 'flak' referred to anti-aircraft fire. American publicists started using 'catching flak' as slang for receiving harsh criticism—and somehow the spelling shifted to 'flack' for PR people, making language history a bit messier than we'd like.
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