What things can’t I trademark?
There are a variety of things which cannot be protected as trademarks - they cannot be federally registered nor will they be afforded protection if you seek court relief. In addition to the reasons that the PTO might reject a trademark application, trademarks are not protectable for the following reasons.
First, you cannot protect generic terms, which are terms that are the actual name of the associated goods or services. Second, you cannot protect marks that are confusingly similar to previously existing trademarks, if you intend to use your mark on similar or related goods and services. Third, you cannot protect a weak mark (a descriptive mark or a mark which otherwise is not inherently distinctive) unless and until it has achieved secondary meaning which shows that the consuming public recognizes the mark as a trademark. Fourth, you cannot protect an abandoned trademark, so if you stop using a trademark and indicate that you do not intend to resume your use, you lose any right to protect it. Finally, while you can protect product design or packaging as trade dress, you cannot protect any functional elements of the design or packaging, only decorative and ornamental elements.