Wikipedia:

"According to OED the word prequel first appeared in print in 1958 in an article by Anthony Boucher in The Magazine of Fantasy & Science Fiction. It appears to have first come into general use in the early 1970s, in which its first known, traceable use is in the original press pack for The Godfather Part II,[1] where it is used to describe the sections of the film which take place before the events of The Godfather"

"Francis Ford Coppola credited George Lucas with devising the term,[citation needed] which Lucas and Steven Spielberg later used to describe their joint project Indiana Jones and the Temple of Doom (which also occurred before the events of the first Indiana Jones film) during publicity for its release. Lucas's own Star Wars prequel trilogy greatly popularized the term in American culture."

I said George Lucas popularized it, but Wanyas was pretty much right beyond that.