Gmc. Folklore a spirit who does mischief and evil, esp. to children: originally a literary character
Origin of erlkingpartial translated, translation of German erlkönig, literally , alder king, from Herder's poem; a misunderstanding by Herder (1778) of Danish ellerkonge, variant, variety of elverkonge, king of the elves
A part-translation of German Erlkönig literally ‘alder-king’, a mistranslation of Danish ellerkonge ‘king of the elves’.