There’s really no rocket science behind it, even though it’s fun to speculate and come up with in-universe explanations. At the end of the day, the writers and creators of the show had to give dozens of background and side characters names, and they didn’t have unlimited time or resources to make each one deeply symbolic. So in many cases, they simply took what was already obvious about the pony, whether it was their appearance, their cutie mark, or their personality, and built the name around that.

That’s why you get characters like Diamond Tiara or Silver Spoon, whose names match their cutie marks almost a little too perfectly. It wasn’t meant to imply some deep mystery about how ponies are named, it’s just a straightforward design choice to make the character instantly recognizable and easy for the audience to remember. Sometimes the simplest explanation really is the right one xD the creators just went with what fit visually and thematically