Before becoming Return of the Jedi, the third Star Wars film was announced as being titled Revenge of the Jedi. This title, and logo was printed on licensee announcements and movie posters, including the Star Wars rerelease poster shown above.
More famously it appeared on the posters above, one without the release date and one with. As most people knows these posters rocketed in value. I sold two copies of the dateless poster, mistakenly thinking that I still had a third, and though the hundreds of dollars I received were a welcome sum in my college years, I'd still rather have one of the posters. I do still have the Star Wars rerelease with the "Revenge" stripe in the corner.
Why the name change? Someone pointed out that by their nature a Jedi would not seek revenge, and so the title was changed to the softer, if more appropriate Return of the Jedi. "Revenge" would finally become part of the title of the third prequel film, essentially Return of the Jedi's counterpart, Revenge of the Sith (2005).
Even before Revenge of the Jedi, the third Star Wars movie was being filmed under an entirely false alternate title: Blue Harvest. The reason for this was twofold. During the making of The Empire Strikes Back, services would raise their prices to benefit from what was assumed a large budget for a big movie. By filming under a pseudonymous title, the production was able to dodge these artificially inflated costs.
The other reason was so that they could film Return of the Jedi without being overrun by vast crowds of Star Wars fans. The production of a movie no one ever heard of would generate little interest. A logo, and catch phrase for this supposed horror movie, starring the same actors as the Star Wars movies, was made and affixed to crew shirts and hats, equipment, stationery, and packages.
Was the ruse a success? Visitors to the scenes of Jabba's sail barge being filmed in the Yuma desert quickly caught on to what was really being filmed, but the crowds were minimal and non-intrusive. Of course the hot, remote, desert location could have helped on its own.
I have one of the Blue Harvest t-shirts packed away.