A troll is a being in Nordic folklore, including Norse mythology. In Old Norse sources, beings described as trolls dwell in isolated areas of rocks, mountains, or caves, live together in small family units, and are rarely helpful to human beings. In later Scandinavian folklore, trolls became beings in their own right, where they live far from human habitation, are not Christianized, and are considered dangerous to human beings. Depending on the source, their appearance varies greatly; trolls may be ugly and slow-witted, or look and behave exactly like human beings, with no particularly grotesque characteristic about them. Trolls are sometimes associated with particular landmarks in Scandinavian folklore, which at times may be explained as formed from a troll exposed to sunlight. Trolls are depicted in a variety of media in modern popular culture. Etymology The Old Norse nouns troll and trǫll (variously meaning "fiend, demon, werewolf, jötunn") and Middle High German troll, trolle "fiend" (according to philologist Vladimir Orel likely borrowed from Old Norse) developed from Proto-Germanic neuter noun *trullan. The origin of the Proto-Germanic word is unknown. Additionally, the Old Norse verb trylla 'to enchant, to turn into a troll' and the Middle High German verb trüllen "to flutter" both developed from the Proto-Germanic verb *trulljanan, a derivative of *trullan. Norse mythology In Norse mythology, troll, like thurs, is a term applied to jötnar and is mentioned throughout the Old Norse corpus. In Old Norse sources, trolls are said to dwell in isolated mountains, rocks, and caves, sometimes live together (usually as father-and-daughter or mother-and-son), and are rarely described as helpful or friendly. The Prose Edda book Skáldskaparmál describes an encounter between an unnamed troll woman and the 9th-century skald Bragi Boddason. According to the section, Bragi was driving through "a certain forest" late one evening when a troll woman aggressively asked him who he was, in the process describing herself: Bragi responds in turn, describing himself and his abilities as a skillful skald, before the scenario ends. There is much confusion and overlap in the use of Old Norse terms jötunn, troll, þurs, and risi, which describe various beings. Lotte Motz theorized that these were originally four distinct classes of beings: lords of nature (jötunn), mythical magicians (troll), hostile monsters (þurs), and heroic and courtly beings (risi), the last class being the youngest addition. On the other hand, Ármann Jakobson is critical of Motz's interpretation and calls