Actually, hobbit can be trademarked. The thing about trademarks is they apply only to one product, goods, or service; one trade. If you want to call your new fMRI machine Hobbit, you can do so, provided nobody else has it trademarked.
You can, if you choose, call a soda Pepsi in your story provided, of course, that you are talking about a Pepsi. The thing about trademarks is that you are not restricted from writing about them in the same way as copyrights.
Many publishers object to trademarks in stories because it is free advertising. In other words, if some else benefits from your story, they should pay for the privilege.