The Erlking’s Daughter, Johann Gottfried von Herder introduced this character into German literature in “Erlkönigs Tochter”, a ballad published in his 1778 volume Stimmen der Völker in Liedern. It was based on the Danish folk ballad “Hr. Oluf han rider” “Sir Oluf he rides” published in the 1739 Danske Kæmpeviser. Herder undertook a free translation where he translated the Danish elvermø (“elf maid”) as Erlkönigs Tochter; according to Danish legend old burial mounds are the residence of the elverkonge, dialectically elle(r)konge, the latter has later been misunderstood in Denmark by some antiquarians as “alder king”, cf Danish elletræ “alder tree”. It has generally been assumed that the mistranslation was the result of error, but it has also been suggested (Herder does actually also refer to elves in his translation) that he was imaginatively trying to identify the malevolent sprite of the original tale with a woodland old man (hence the alder king).