McCarthyism:  A term derived from the name and actions of Joseph McCarthy, senator from Wisconsin, who, playing on people's fear of communism, rose to prominence in the 50s by saying that he had the names of 57 “known communists” working for the State Department.  Along with the House Un-American Activities Committee (HUAC), he is responsible for the “witch hunt” hysteria of the 50s, where the question “Are you now or have you ever been a member of the communist party” signaled the end of a career.

His name (turned into an –ism) has become a shorthand for hysteria based on rumor and distortion.