Copyright doesn't apply to created proper nouns. They're too short. Maybe some extreme example might be considered copyrightable, but generally it's a work or creative design, something that has meaning in itself, that's copyrightable. A proper noun without context means next to nothing.
What is copyrighted is a character, or potentially a detailed fictional entity behind the proper noun. If you make a story about a character with similar identifiable traits to Harry Potter, for instance, that violates Rowling's copyright on the character. Even if your character isn't named Harry Potter, but using the same name would make the case super easy to win.
They could be registered as trademarks, but then the estate would have to show that the use of the trademark was confusing or deceptive. I don't see how it could be, unless someone believes we live in Middle Earth, or unless Tolkien's estate used those names for companies (which would have to do things, not just be paper or shell companies) or products. They'd still have to show that the other companies' use of the names was confusing or deceptive; if the estate's companies or products weren't in the tech space, that might be difficult.
What is copyrighted is a character, or potentially a detailed fictional entity behind the proper noun. If you make a story about a character with similar identifiable traits to Harry Potter, for instance, that violates Rowling's copyright on the character. Even if your character isn't named Harry Potter, but using the same name would make the case super easy to win.
They could be registered as trademarks, but then the estate would have to show that the use of the trademark was confusing or deceptive. I don't see how it could be, unless someone believes we live in Middle Earth, or unless Tolkien's estate used those names for companies (which would have to do things, not just be paper or shell companies) or products. They'd still have to show that the other companies' use of the names was confusing or deceptive; if the estate's companies or products weren't in the tech space, that might be difficult.