Wraith

Wraith is a Scottish dialectal word for "ghost", "spectre" or "apparition". It came to be used in Scottish Romanticist literature, and acquired the more general or figurative sense of "portent" or "omen". In 18th- to 19th-century Scottish literature, it was also applied to aquatic spirits. The word has no commonly accepted etymology; OED notes "of obscure origin" only. An association with the verb wraith was the etymology favored by J.R.R Tolkien. Tolkien's use of the word in the naming of the creatures known as the Ringwraits has influenced later usage in fantasy literature.