There’s also a town in Washington State called Vader. That’s why it’s going to have to be some name like “Sdaarbt Ffoedyr,” that someone writing in English would not come up with, and not a name that sounds like it could be English, even if no one actually has that name, like “Beru Skywalker.” Calling a planet “Vulcan” doesn’t take much imagination. Being the second person to call one “Kashyyyk” suggests that someone got a peek at an unpublished or unproduced work.
It’s really not the name itself: it’s that the use of it is proof of a larger violation.
I really do not think this is true, but if you have a cite that the use of an unusual name that is not protected by trademark in two different creative works is proof that one of the authors violated intellectual property law then I’d be curious to see it.
If the two works were substantially similar then the use of the same name might be taken as evidence of wrongdoing, but the name is the only detail from Star Wars that Marty shared with young George. Even if George uses the name in his fiction, a story based on his encounter with “Darth Vader” isn’t going to bear much resemblance to the Star Wars movies.