The word "Mnemonic Device" does not do the concept of a memory trigger justice. I rather use the direct and literal translation of "Mnemonic Device" from the German language "DONKEY BRIDGE", which comes from "Eselsbrücke".
A donkey bridge can be anything that will trigger your memory to remember something. It can by an acronym, silly associations, rhymes, as well as music or an image that you have in your mind. For children it seems to be true that the more bizarre the donkey bridge the better...