I mean I'm no expert and I have no idea how much this is going to help, but they're very similar words. In the dictionary, they all have at least one definition that is the same being "a group of three", which could lead someone to believe that they could use all three words to mean a musical group of three, even though they might not be able to due to how the words are perceived. They might essentially mean the same thing in the dictionary, but society has used these words for different reasons, I guess.