Jedi

wiktionary

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Coined by American filmmaker George Lucas as early as 1973 (in the manuscript Journal of the Whills) and first used in his 1977 film Star Wars. Said to have been adapted from Japanese 時代劇(jidaigeki, “"period drama" motion pictures about  samurai”), or perhaps inspired by the words Jed (King) and Jeddak (Emperor) in the Barsoom series by Edgar Rice Burroughs, which Lucas had considered adapting to film. 

etymonline

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Jedi (n.)

characters in the "Star Wars" sagas, 1977, apparently an invented word.