You are right. I think emoji tend to develop meaning by being repeatedly used in a context. Their names are titles or identifiers but not helpful for meaning.
Which kinda sucks, because if I don't know what a word means, I go to the dictionary. Someone using a word wrong is going to really throw me off if their usage doesn't match the dictionary definition. If I don't know what an emoji means, I'll look at the title. And it's likely something very different than the emotion trying to be portrayed.