Dwarf

In Germanic mythology, a dwarf is a human-shaped entity that dwells in mountains and in the earth, and is variously associated with wisdom, smithing, mining, and crafting. Dwarfs are sometimes described as short and ugly, although some scholars have questioned whether this is a later development stemming from comical portrayals of the beings. Dwarfs continue to be depicted in modern popular culture in a variety of media.

Etymology and usage 
The modern English noun dwarf descends from the Old English dweorg. It has a variety of cognates in other Germanic languages, including Old Norse dvergr and Old High German twerg. According to Vladimir Orel, the English noun and its cognates ultimately descend from Proto-Germanic *đwergaz.A different etymology of dwarf traces it to Proto-Germanic *dwezgaz, with r being the product of Verner's Law. Anatoly Liberman connects the Germanic word with Modern English dizzy: allegedly, dwarfs inflicted mental diseases on humans, and in this respect did not differ from elves and several other supernatural beings. 

Beyond the Proto-Germanic reconstruction, the etymology of the word dwarf is highly contested. Scholars have proposed theories about the origins of the being by way of historical linguistics and comparative mythology, including that dwarfs may have originated as nature spirits, as beings associated with death, or as a mixture of concepts. Competing etymologies include a basis in the Indo-European root *dheur- (meaning 'damage'), the Indo-European root *dhreugh (whence, for example, modern English dream and German Trug'deception'), and comparisons have been made with Sanskrit dhvaras (a type of "demonic being").

Modern English has two plurals for the word dwarf: dwarfs and dwarves. Dwarfs remains the most commonly employed plural. The minority plural dwarves was recorded as early as 1818, but it was popularized by the fiction of philologist and author J. R. R. Tolkien, originating as a mistake (hypercorrection) and employed by Tolkien since some time before 1917 (for Tolkien's beings, see Dwarf (Middle-earth)).Regarding the plural, Tolkien wrote in 1937, "I am afraid it is just a piece of private bad grammar, rather shocking in a philologist; but I shall have to go with it".
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https://en.wikipedia.org/wiki/Dwarf_(mythology)