Elves By Jean-Baptiste Monge

In early modern and modern folklore, they become associated with the fairies of the 19-century Romantic portrayal of English folklore and assume a diminutive size, often living underground in hills or rocks, or in wells and springs. 19th-century Romanticism attempted to restore them to full stature, often depicting them as very young, probably adolescent (lack of facial hair on male elves), men and women of great beauty. From their depiction in Romanticism, elves entered the 20th-century high fantasy genre in the wake of the publications of J. R. R. Tolkien, especially the posthumous publication of his Silmarillion where Tolkien's treatment of the relation of light elves, dark elves, black elves and dwarves in Norse mythology is made explicit. The elf is now-and has been for years-associated with Christmas acting as "Santa's little helpers."
The name elf is from Old English ælf (plural ylfe), ultimately from a Common Germanic alboz (also albiz), corresponding to Old Norse álfr, Old High German alb. It survives as an element in given names such as English and German Alfred, Alfwin, Elfreda, or Scandinavian Alfhild, Alvar. There are no obvious cognates outside of Germanic, but some have compared the ṛbhu, a type of genii in Hindu mythology.