A name cannot enjoy copyright protection. The US Copyright Office says so in their circular Copyright Protection Not Available for Names, Titles, or Short Phrases, specifically
Even if a name, title, or short phrase is novel or distinctive or
lends itself to a play on words, it cannot be protected by copyright.
The U.S. Copyright Office cannot register claims to exclusive rights
in brief combinations of words such as...
followed by various forms of names. A name can enjoy trademark protection. The easier case is to look up the name to see if it is registered. The US Patent and Trademark Office has a search page allowing you to look stuff up. More challenging is the common law trademark, which need not be registered. But as far as I can tell, a common law trademark is about a business brand name, and wouldn't arise from using a name from a novel.
To take a concrete example, the fictitious name "Galt" figures in quite a number of registered trademarks (none having been registered by the author).