In old Germany, "elf" was a name applied to any kind of supernatural spirit, especially one that inhabited fields or forests.
In Scotland, England, and Scandinavia, "elf" was another name for a member of the fairy folk. Then, as fairy lore developed and became more intricate and complex, with levels and classes within their supernatural ranks, the English designated elves as smaller members of the fairy population and the Scots gave the title of elf to those beings that were generally of human size. Things changed a bit in Scandinavia, as well, when the people there began to distinguish two categories of elves-the benign ones and the dastardly ones.
Scandinavians also envisioned two principle divisions of the beings. There were the lovely, charming elves, who easily passed for humans and who loved to join in folk dances and in village parties. These elves, especially the females of the bunch, could easily seduce any human male into obeying their will. The male elves, though appearing handsome and dashing in the firelight of a village festival, would usually be exposed as squat and ugly when moonlight struck them in the forests. The Danes also noticed that even the attractive elves occasionally betrayed themselves with a long cow-like tail that popped out of their dress or trousers.
In contemporary presentations, elves are usually portrayed as jolly creatures, humanlike in appearance, but extremely diminutive in size, that love teasing humans and playing pranks on them. Of course there's that "right jolly old elf," Santa Claus who brings good children toys at Christmas time.
Traditionally, the fairies are a race of beings, the counterparts of humankind in physical appearance but, at the same time, nonphysical or multidimensional. They are mortal, but lead longer lives than their human cousins.
Years ago, I was sternly advised that if I should ever have an encounter with a fairy and wish to survive basically intact, there are two rules I must remember: 1) Don't you dare ask its name. 2) Don't you dare call it a fairy. According to those who speak the Gaelic tongue of Scotland and Ireland, the wee folk prefer to be known as sidhe (also spelled sidh, sith, sithche and pronounced "shee"). There is disagreement as to the exact meaning of sidhe. Some say that it refers to the mounds or hills in which the supernatural folk abide. Others say that it means, "the people of peace," and that is how the sidhe generally behave toward humans-except for those seemingly incurable elfin traits of kidnapping human children and shape-shifting into a seemingly endless variety of forms in order to work mischief.
Alexander Pope wrote lovely passages idealizing fairies. Sir Walter Scott emphasized the beauty of the fairy realm and the struggle of the fairies to achieve humanlike souls. William Butler Yeats had a nearly obsessive interest in the paranormal and strongly believed in fairies. And it was the creator of Sherlock Holmes, Sir Arthur Conan Doyle himself, who came to the defense of Elsie Wright and Frances Griffiths in the famous and controversial Case of the Cottingly Fairies in 1917.
Doyle theorized that the fairies are constructed of material that emits vibrations either shorter or longer than the normal spectrum visible to the human eye. Clairvoyance, he believed, consists, at least in part, of the ability to see these vibrations.
In most traditions, especially in the British Isles and Scandinavia, the fairy folk were supernormal entities that inhabit a magical kingdom beneath the surface of the earth. In all traditions, the fairy folk are depicted as possessing many more powers and abilities than Homo sapiens, but, for some unexplained reason, they are strongly dependent on human beings-and from time to time they seek to reinforce their own kind by kidnapping both children and adults. Tales of folk being abducted by smallish beings did not begin in the last few decades with accounts of the "Grays" from UFOs.
The Fey have never been popularly conceived of as spirits, although some theologians have sought to cast the fairies in the role of the rebellious angels that were driven out of heaven during the celestial uprising led by Lucifer.
Most of the ancient texts declare that the "gentry," as they are often called, are of a middle nature, "between humans and angels." Although they are of a nature between spirits and humans, they can intermarry with humans and bear half-human children.
C. S. Lewis, author of many classic books on spiritual matters, once suggested that the wee folk are a third rational species.
1) The angels are highest, having perfect goodness and whatever knowledge is necessary for them to accomplish God's will;
2) Humans, somewhat less perfect, are the second;
3) Fairies, having certain powers of the angels but no souls, are the third.
On the other hand, Medieval theologians favored three quite different theories to explain the origin of fairies:
1) They are a special class of demoted angels;
2) They are a special class of the dead;
3) They are fallen angels.