You might think that common words and generic terms can't be used as trade marks. That's true, in theory, in some cases, in some jurisdictions. The image shown, from the US Patent and Trademark Office
TESS search system shows that words do get issued as trade marks. Some of these words might seem more or less common, others seem more or less generic, others seem more or less descriptive.
You might argue about whether this is
There is a process for legal argument between parties who disagree on one or more specific trade marks. That process will vary depending on your jurisdiction, and that of the other party, and of the trade mark registering body. That process generally involves paying lawyers.