“Darth Vader” and “Vulcan” are not hard things to come up with. Vulcan is the Roman god of fire, and “Darth Vader” sounds like “Dark Invader,” which was always how I thought Lucas came up with it, even when I was a kid. I know someone else who always thought it was “Death Invader.” Regardless, the point is, it sounds very English-y.
In early Star Wars, everything sounded like something: “droid” was from “android,” “Tusken raiders” used animals that had tusks. I personally think that the whole “parsec” sounding like it’s being used as a unit of time, when it’s a unit of distance happened because Lucas wasn’t familiar with the term, and thought he made it up. After the first movie, and the parsec debacle, Lucas started using words that didn’t sound like they could be English, like “Kashyyyk.”
It isn’t that hard to imagine that two different people could come up with a name like “Darth Vader.” Whether the source was “Dark Invader,” or “Death Invader” (or a portmanteau) it follows English morphological and orthographic rules. Even if McFly and Lucas both produced works independently that had a character with the name, it would be simple to get a linguist to testify that two people could invent the name independently, with no plagiarism involved.
There have actually been suits like this.
Someone who wrote a book called Rah and the Muggles, the plot of which bears no resemblance to Harry Potter, other than, it has some magical elements, tried to sue JK Rowling. I don’t know exactly what came of it, but I remember at the time thinking that “muggle” is exactly the kind of word an author writing in English, making up a word would come up with. It’s a word that could be English, but isn’t (or, wasn’t). It’s similar to muddle, and juggle, both of which are perfectly good English words, and it’s quite reasonable that two authors might come up with “muggle” independently. It’s not like “pfuiadzk,” something that couldn’t be an English word, so if two English-language authors both came up with it, you’d have a better case for plagiarism.
So no, I don’t think it would mess up Star Wars. If McFly came out with a book with “Darth Vader” first, Lucas would just have to come up with another name, and otherwise, the story would be different, unless you think some butterfly effect would cause the name change of necessity to alter Lucas’s story. Personally, I don’t think so. If Lucas used the name first, McFly would come up with another name.
And, FWIW, this could be McFly’s first book, but that doesn’t mean he hasn’t been making a living as a writer. He could have been publishing short stories, and contributing to TV scripts, or working as an editor, or copy writer. He could have been a journalist, or even a science writing consultant-- someone who helps scientists write articles for lay people. He could have been a “novelizer,” the guy who writes novels from movie scripts, so he may have had straight to paperback books under his name, but they weren’t his original work-- this was the first book that was all his own. Hardly anyone comes out of the woodwork with a full-blown book, who has never written anything for the public before.
