You can't copyright a name. That's what trademark law does. While choosing a good name certainly takes some creative effort, it is not equivalent in the eyes of the law to a creative expression like a short story, song, or computer program.
Yeah. I feel bad for the guy who developed Go!, but I also totally understand Google's decision not to change the name.
Swift, Go are somewhat obvious names for a programming language (they express speed and action), and if you keep in mind *every smaller languages, it's almost impossible to come up with a name that nobody used as a programming language.
Sure, don't start a new programming language and call it Python or Java, but how about Falcon, Cheetah, Quick, etc? I never heard about any of them, but I'm sure there exist somewhere a programming language written by a solo developer that uses one of these names.
Falcon was also a computer system from Atari. Cheetah is also at least a computer system, a brand of drive, and a template system for Python. I don't know of languages called Cheetah or Quick. They may exist. "Quick" was part of the name for multiple programmers' tools and language implementations from Microsoft - QuickBasic, QuickC, QuickPascal, QuickAssembler... maybe more. They competed with the Borland Turbo C, Turbo Pascal, Turbo Assembler, Turbo Prolog, and Turbo Basic languages. This was back before MS switched to Visual C++, VisualBasic, etc.
Whether something is a big deal has nothing to do with whether there was a court case about it. Google behaved really poorly here. They should have changed the name. That has nothing to do with any law.
Organizations with very deep pockets have pursued copyright cases against Google. Mostly unsuccessfully because Google's pockets are deeper and litigation is expensive.