Everyone knows that the cute, fuzzy critters from Return of the Jedi are called the Ewoks... but how does everyone know that? If you watch the movie carefully, you'll notice that they never use the name anywhere. So where does the name come from?
George Lucas was sued by a guy named Dean Preston, who claimed
he invented the Ewoks in a script called "Space Pets" that he wrote in 1977 and mailed to Lucas in 1978.
Lucas testified in court that
he created the Ewoks in his original 1974 draft of "The Star Wars" and came up with the name by reversing the syllables of the character he called Wookie and rhyming it with the Northern California Indian tribe known as the Miwok (pronounced: mee-walk).
The name "Ewok" only appeared in the script directions, the novelization, the movie's credits, and other spin-off and promotional materials.
No idea when they first appeared but there were two movies that featured Ewoks in them that came out shortly after the movie did. Here are some links.
Also according to wikipedia,
In the film, the name "Ewok" is never actually spoken, but it appears in both the script and the closing credits.