Speaking of trolls in music, if you've ever sung "Deck the Halls" you've come across the last line: "Troll the ancient yuletide carol", which means sing it in rounds. The Germanic root troll became a verb in Old French for "to wander about", and then came back into Middle English, where it was applied to music (the melody wanders about the groups singing) and to fishing (trailing a line and moving the boat about).