The Danish peasantry give the following account of their EllefoIk or Elve-people.
The Elle-people live in the Elle-moors. The appearance of the man is that of an old man with a low-crowned hat on his head; the Elle-woman is young and of a fair and attractive countenance, but behind she is hollow like a dough-trough. Young men should be especially on their guard against her, for it is very difficult to resist her; and she has, moreover, a stringed instrument, which, when she plays on it, quite ravishes their hearts. The man may be often seen near the EIle-moors, bathing himself in the sunbeams, but if any one comes too near him, he opens his mouth wide and breathes upon them, and his breath produces sickness and pestilence.
But the women are most frequently to be seen by moonshine; then they dance their rounds in the high grass so lightly and so gracefully, that they seldom meet a denial when they offer their hand to a rash young man. It is also necessary to watch cattle, that they may not graze in any place where the Elle-people have been; for if any animal come to a place where the Elle-people have spit, or done what is worse, it is attacked by some grievous disease which can only be cured by giving it to eat a handful of St. John’s wort, which had been pulled at twelve o’clock on St. John’s night.
It might also happen that they might sustain some injury by mixing with the Elle-people’s cattle, which are very large, and of a blue colour, and which may sometimes be seen in the fields licking up the dew, on which they live. But the farmer has an easy remedy against this evil; for he has only to go to the Elle-hill when he is turning out his cattle and to say, “Thou little Troll!
Source
THE FAIRY MYTHOLOGY BY THOMAS KEIGHTLEY (1850)