Google's attempt to trademark the word "Glass" is being met with opposition at the US Patent and Trademark Office, reported The Wall Street Journal Thursday. The term's generic nature and the potential for customer confusion about other products that involve the word "Glass" are two of the office's biggest concerns, but Google continues to push back. The company has already successfully trademarked "Google Glass."

Google originally submitted the application in July 2013 for the word "Glass" styled in a particular font as branding for its Google Glass smart glasses. The USPTO responded in the fall, saying there are two problems with trademarking "Glass."

The first is that the word is "merely descriptive" and that the product does not actually contain any glass (it's made of titanium and plastic). Second, the word is too similar to pre-existing trademarks, making confusion "as to the source of the goods" likely, the USPTO said.

Google responded on March 20 to the examiner's objections with a 1,928-page document demonstrating the variations of "Glass" trademarks that customers are currently able to distinguish between. Google also submitted the argument that "the sophistication of the purchasers of goods offered under the respective marks weight against finding a likelihood of confusion"—essentially, people who would buy Google Glass are too smart to not know what "Glass" refers to.

To defend against the "merely descriptive" point, Google cites a number of cases where the USPTO has granted trademarks to products that are not made of the materials they reference—for instance, Platinum Micro, Inc., a computer hardware company.

After the arguments, the document's remaining 1,903 pages consist of various articles that use the terms "Google Glass" and "Glass."

The Journal notes that Google doesn't need a trademark to drop the "Google" and have a product simply called Glass. But without one, companies could infringe on the name, and Google would have a hard time defending itself.