ThoughtWorks first released the commercial product that would become Go in 2008. It was rebranded later, shortly after the public announcement of Golang. Yes, it was a confusing move, but at the time there was no reason to believe that a programming language might conflict with a continuous delivery tool. Golang has produced a large and robust community, so of course it's confusing now. But it didn't come out of nowhere.
Might be hard to do, since it has been around for a while, but here's the Github issue on the project about the name: https://github.com/gocd/gocd/issues/131
apparently Thoughtworks has been building the Go continuous delivery tool as a custom product from even before Google made Go! I think the word "GO" hasn't been trademarked yet.
Speaking of golang (go), this slide [0] lists breaking new ground in programming language research as a non-goal. That may include language name research.