A troll is a member of a fearsome humanoid race from Scandinavian folklore, and its predecessor Norse mythology, as in "The Three Billy Goats Gruff (http://www.surlalunefairytales.com/billygoats/)," the well-known Scandinavian folk tale in which a troll living under a bridge torments some billy goats that want to cross. Grendel in the poem Beowulf is a closely similar creature. The word "Troll" is possibly derived from an old norse word meaning magic, cf. Swedish "Trolla", Danish "Trylle" (Perform magic tricks).