The word wraith is a Scottish dialectal word for "ghost, spectre, apparition". It came to be used in Scottish Romanticist literature, and acquired the more general or figurative sense of "portent, omen". In modern fantasy literature, it usually designates dangerous and evil beings following use of the word in J.R.R. Tolkien's Ringwraiths.Etymology
The word "wraith" according to the OED first attested in 1513, in Gavin Douglas' translation of the Aeneid with a meaning of both "ghost, apparition of a deceased person" and "an immaterial or spectral appearance of a living being".
In 18th- to 19th-century Scottish literature, it was also applied to aquatic spirits. In 19th-century usage, it came to be used in a metaphoric sense to refer to wraith-like things and to portents in general.
The word has no commonly accepted etymology; OED notes "of obscure origin" only. An association with the verb writhe was the etymology favoured by J. R. R. Tolkien.
Modern Literature
Tolkien's use of the word in the naming of the creatures known as the Ringwraiths has influenced later usage in fantasy literature.
The word "wraith" is also used in modern fiction to signify the shifting wraiths of T.A. Barron's book series The Lost Years of Merlin and the mortiwraiths of Wayne
Thomas Batson's "The Door Within Trilogy". Whereas the shifting wraith is a bestial, snake-like predator able to change itself into the form of any animal, albeit always having a feature uncharacteristic thereof, the mortiwraith is an anthropomorphically intelligent, gigantic, cave-dwelling, extremely photosensitive, but also snake-like predator having creased, furry ears, poisonous blood, and many clawed legs, whose quantity increases with the passage of every five years. The use of the word "wraith" for either of these is not explained in either story, though it may relate to the word "writhe".
The Wraith plays a part in the novel Stargazer by Claudia Gray, the second instalment in the Evernight series.
In the War of Light and Shadows series by Janny Wurts the Mistwraith is a major plot device. The Mistwraith was in fact a mist made up of countless individual wraiths that in a collective swarm appeared to be mist. The mistwraith blocked out the bulk of sunlight of Athera the main world of the sequence and made the world constantly gloomy.
Within the Land, the world of Stephen Donaldsons series focusing on Thomas Covenant the Unbeliever, the wraiths were beings that resembled candle flames without the candle.
The Wraith are also a fictional species in the series Stargate Atlantis.
The "wraith" - "remnant wraith" or "death wraith" appears also in the popular online game Lineage 2. The "remnant wraith" are high level undead located near Alien Totem on Kamael Island and the "Death Wraith" appears in catacombs/necropolis as a high level Lilim/Nephilim commander.