"Drow, n., [scot.]  A tiny elf which lived in caves and forged magic metal work."  Webster's Unabridged Dictionary (1970 edition)

"Drow, n.,  Mythology and folklore of the Shetland Islands.  A troll-like monster."  Chambers Dictionary (1972 edition)

"Trow, n.,  In the folkloric traditions of the Orkney and Shetland islands, a trow (alternatively trowe or drow) is a small, troll-like fairy creature...  Trows are nocturnal creatures; venturing out of their 'trowie knowes' (earthern mound dwellings) solely in the evening, they often enter households as the inhabitants sleep.

"Dökkálfar or dark elves, a type of elf in Norse mythology."

"Svartalfar or black elves, a type of elf in Norse mythology."

"... should exhibit a darker and more malignant character, than the elves that revel by moonlight... Such possession of supernatural wisdom is still imputed, by the natives of the Orkney and Zetland islands, to the people called Drows ... they appeared in deep caverns and among horrid rocks; as also, that they haunted the places where murders, or other deeds of mortal sin, had been acted... Their elves did not avoid the society of men, though they behaved to those who associated with them with caprice, which rendered it dangerous to displease them...  A King, more frequently a Queen, of Fairies, was acknowledged; and sometimes both held court together...  The reason assigned for this kidnapping of the human race, so peculiar to the elfin people, is said to be that they were under a necessity of paying to the infernal regions a yearly tribute out of their population, which they were willing to defray by delivering up to the prince of these regions the children of the human race, rather than their own..."
         ~ Sir Walter Scott (1830) Letters on Demonology and Witchcraft, Letter IV (pg118).