Meaning

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

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

noun a fisherman's lure that is used in trolling

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