In medieval Germanic cultures, elves seem generally to have been thought of as a group of beings with magical powers and supernatural beauty, ambivalent towards everyday people and capable of either helping or hindering them. In Old Norse mythological texts, elves seem at least at times to be counted among the pagan gods; in medieval German texts they seem more consistently monstrous and harmful.
In English literature of the Elizabethan era, elves became conflated with the fairies of Romance culture, so that the two terms began to be used interchangeably. German Romanticist writers were influenced by this notion of the 'elf', and reimported the English word elf in that context into the German language. In Scandinavia, probably through a process of euphemism, elves often came to be known as (or were conflated with) the beings called the huldra or huldufólk. Meanwhile, German folklore has tended to see the conflation of elves with dwarfs.
The "Christmas elves" of late Terran Pre Astro popular culture were of relatively recent tradition, popularized during the late 19th century CE in the United States. Elves entered the 20th century high fantasy genre in the wake of works published by authors such as J. R. R. Tolkien.