this theory "unsupported by any convincing evidence". Ármann highlights that the term is used to denote various beings, such as a jötunn or mountain-dweller, a witch, an abnormally strong or large or ugly person, an evil spirit, a ghost, a blámaðr, a magical boar, a heathen demi-god, a demon, a brunnmigi, or a berserker. Scandinavian folklore Later in Scandinavian folklore, trolls become defined as a particular type of being. Numerous tales are recorded about trolls in which they are frequently described as being extremely old, very strong, but slow and dim-witted, and are at times described as man-eaters and as turning to stone upon contact with sunlight. However, trolls are also attested as looking much the same as human beings, without any particularly hideous appearance about them, but living far away from human habitation and generally having "some form of social organization"—unlike the rå and näck, who are attested as "solitary beings". According to John Lindow, what sets them apart is that they are not Christian, and those who encounter them do not know them. Therefore, trolls were in the end dangerous, regardless of how well they might get along with Christian society, and trolls display a habit of bergtagning ('kidnapping'; literally "mountain-taking") and overrunning a farm or estate. Lindow states that the etymology of the word "troll" remains uncertain, though he defines trolls in later Swedish folklore as "nature beings" and as "all-purpose otherworldly being[s], equivalent, for example, to fairies in Anglo-Celtic traditions". They "therefore appear in various migratory legends where collective nature-beings are called for". Lindow notes that trolls are sometimes swapped out for cats and "little people" in the folklore record. A Scandinavian folk belief that lightning frightens away trolls and jötnar appears in numerous Scandinavian folktales, and may be a late reflection of the god Thor's role in fighting such beings. In connection, the lack of trolls and jötnar in modern Scandinavia is sometimes explained as a result of the "accuracy and efficiency of the lightning strokes". Additionally, the absence of trolls in regions of Scandinavia is described in folklore as being a "consequence of the constant din of the church-bells". This ringing caused the trolls to leave for other lands, although not without some resistance; numerous traditions relate how trolls destroyed a church under construction or hurled boulders and stones at completed churches. Large local stones are sometimes described as the product of a troll's