Trolls lurk under bridges waiting to eat children, threaten hobbits in Middle-Earth, and invade the dungeons of Hogwarts. Often they are depicted as stupid, slow, and ugly creatures, but they also appear as comforting characters in some children' s stories or as plastic dolls with bright, fuzzy hair. Today, the name of this fantastic being from Scandinavia has found a wider reach: it is the word for the homeless in California and slang for the antagonizing...