yippie

noun

1. a member of a group of radical, politically active hippies.

1968, acronym from fictitious “Youth International Party,” modeled on hippie. On December 31, 1967, Abbie [Hoffman], Jerry [Rubin], Paul Krassner, Dick Gregory, and friends decided to pronounce themselves the Yippies. (The name came first, then the acronym that would satisfy literal-minded reporters: Youth International Party.) [Todd Gitlin,” The Sixties,” 1987, p.235]