Andersen, H. C. Uddrag fra Danish Popular Legends. By Hans Christian Andersen

There is an old popular saying that our Lord, when he expelled the fallen angels, let some of them drop down upon the hills, where they live still, and are called »Bjergfolk« (mountain goblins), or »Trolde« (imps). They are always afraid, and flee away when it thunders, which is for them a voice from heaven. Others fell down in the alder moors; they are called »Elverfolk« (alder folks), and among them the women are very handsome to look at, but not to trust; their backs are also hollow, like a dough-trough. Others fell down in old farms and houses; they became dwarfs and »Nisser« (elves). Sometimes they are wont to have intercourse with men, and a great many stories about them are related which are very strange.