[Laremere]

I was going to say the terminology comes from inside Google, where afaik go links were invented. However, yeah, that's straight up a trademark. You'd need a lawyer to know whether the trademark would survive litigation, and whether the s on those trademarks makes a material difference. (OP isn't plural, those trademarks are)

[vineyardmike]

How can they defend a trademark that people used (at Google) before them?

[sullivanmatt]

A trademark is not a patent, you don't need to prove you were first to have "the idea". [IANAL] It's the first to use the term in a commercial context, which Google has not.