A mnemonic is a way of remembering something. A heuristic is a fallible way of solving a problem or making a decision.
I don’t like the habit people have of providing a mneumonic as a way of teaching something when the underlying information isn’t apparent. I could teach FEW HICCUPPS to someone, even what the letters stood for, and they’d be no better off. It’s only when you know that “history” means “the current version should be like the previous versions” that it becomes useful.
I once tweeted some mneumonics to satirise this concept.