"Yippie" was coined by Paul Krassner in his New York-based publication, The Realist, in 1967. "Yippie" is mainly of historical interest today.
(Oxford English Dictionary)
yippie, Yippie
orig. U.S.
[f. the initials of Youth International Party + -IE, influenced by HIPPIE, HIPPY n. and a.]
A member of a group of politically active hippies, orig. in the United States.
1968 Time
http://en.wikipedia.org/wiki/Youth_International_Party
The Youth International Party (whose adherents were known as Yippies, a variant on "Hippies" which is also used today to designate the surviving circle of activists who came out of the now-defunct YIP) was a highly theatrical political party established in the United States in 1967. An offshoot of the free speech and anti-war movements of the 1960s, Yippies presented a youth-oriented countercultural alternative to the strait-laced earnestness often associated with representatives of those movements. They employed media-savvy gestures—such as advancing a pig ("Pigasus the Immortal") as candidate for President in 1968—to mock the social status quo.
The Yippies had no formal membership or hierarchy: Abbie Hoffman, Anita Hoffman, and Paul Krassner were among the founders of the Yippies (according to his own account, Krassner coined the name). Other activists associated with the Yippies include Jerry Rubin, Stewart Albert, Dick Gregory, Ed Sanders, Phil Ochs, and David Peel.
Abbie Hoffman and Jerry Rubin became the most famous Yippies—and bestselling authors—in part due to publicity surrounding the five-month Chicago Seven Conspiracy trial of 1969.
(...)
A YIP-related newspaper, The Yipster Times was founded by Dana Beal in 1972 and published in New York City. It changed its name to Overthrow in 1979.
Yippies in the new millennium
The Yippies led by Beal, with their headquarters at 9 Bleecker Street in lower Manhattan, have continued as a small movement into the early 2000s. They no longer publish a newspaper but are known for their annual marches in New York City to legalize marijuana.
August 1967, The Realist, article written by Paul Krassner, pg. 21, col. 2:
Coincidental with the Democrats' Convention there's going to be a Youth International Party -- YIP -- and Chicago will be invaded by a mass of yippies.
You've just witnessed the birth of a word.

