Wight is an obsolete word for a "human" or other intelligent "being" and derives from the same root as forms of to be, such as was and were. In nodern German "Wicht" means both "small person, dwarf" as well as "unpleasant person".
The word Wight is used only comparatively recently to give an impression of archaism and mystery, for example in the works of J. R. R. Tolkien, where are corpses with a part of their decayed soul. Probably inspired by Scandinavian Mythology, as Tolkien also used the word to denote human-like creatures, such as Elves or ghosts ("wraiths") - most notably the undead Barrow-Wights.
Some subsequent writers seem to have been unaware that the word did not actually mean ghost or wraith, and so many works of fantasy fiction, role-playing games (such as Dungeons & Dragons) and video games use the term as the name of spectral creatures resembling Tolkien's Barrow-wights.
From the same Germanic root, the Icelandic word vættr designates some kind of supernatural being. At times, even the gods of Norse mythology are called vættir. However, the most common usage appears to be in reference to sjóvættir (sea-wights) and landvættir (land-wights). Landvættir were said to be chthonic beings of specific farms and wild places. When Norse seafarers approached land, they reportedly took off the carved dragons from the bows of their longships, so as not to frighten or insult the landvættir as they might be bringers of bad luck.
In modern day Iceland, stories still abound of the landvættir (also known as huldufólk, the hidden people, often hard to distinguish from álfafólk, i.e. elves). It is said that work crews building new roads will sometimes divert the road around particular boulders which are known to be the homes of these people.
Scandinavian folklore features a class of beings similar to the Old Norse landvættir. They are known by many names, although the most common are vättar in southern Sweden, vittra in northern Sweden and huldrefolk in Norway (though it should be noted that the singular vittra and huldra, respectively, refer to a solitary and quite different being). Henceforth, they are referred to as "wights" in this article. The Norwegian vetter is used much in the same way as the Old Norse vættir, whereas the corresponding word in Swedish or Danish is väsen or væsen (being), also akin to was and were.
Many aspects of the dwarves in Norse mythology lived on in the Scandinavian belief in wights. They were thought to be similar in appearance to humans, even strikingly beautiful, but smaller, often clad in grey and living underground. Therefore, they were also called de underjordiske (the subterranean ones). The cautious peasant in old Scandinavia should always warn the wights before spilling hot water on the ground, or else grave retribution, such as disease, accidents or killed livestock, was to be expected. Wights had their own minute cattle, from which they nevertheless got a tremendous amount of milk. They were also described as having the ability go invisible from human sight whenever they wished to, as well as transform into animals (toads being a disguise of choice). This made them hard to observe, save brief glimpses; children, however, were thought to be much more capable to see through the magic of the wights.
The tomte or nisse is a solitary vätte, living on the farmstead. He is usually benevolent and helpful, which can not be said about a mischievous illvätte. However he can cause a lot of damage if he is angry, such as killing livestock.
The stories about the Norwegian huldrefolk have taken on many aspects usually associated with Trolls in southern Sweden and Denmark. For example, the women of the huldrefolk were said to be quite beautiful, with the one exception being their long cow-like tails. She was in Swedish called the "skogsrå". They take great pains to hide these tails so as not to be detected for what they are. They are also often described as having a back like a hollow log. The Huldra often attempted to seduce men in the forest or mountains. Moreover, the huldrefolk sometimes kidnapped infants and replaced them with their own ugly huldrebarn (changeling).
The collected Norwegian [olk tales of Peter Christen Asbjørnsen and Jorgen Moe contain many stories about huldrefolk.