Meaning

noun (Scandanavian folklore) a supernatural creature (either a dwarf or a giant) that is supposed to live in caves or in the mountains

verb circulate, move around

noun a partsong in which voices follow each other; one voice starts and others join in one after another until all are singing different parts of the song at the same time

originThe verb is derived from Middle English trollen (“to go about, wander; to move (something) to and fro, rock; to roll; to turn”) [and other forms], of uncertain origin; perhaps in part from Old French troller (“to run here and there; to walk aimlessly, ramble, stroll; (hunting) to wander about looking for game”) (modern French troller); further etymology uncertain, yet probably from or related to…

Etymology from Wiktionary, CC BY-SA 3.0