In medieval sources, the Swan Knight invariably appears as a character imbued with a sacred nature. The initial section of the “Swan Knight plot”, which developed in the French tradition, is dedicated to his miraculous birth. Presumably, the plot section about the Swan Knight’s birth originates from folklore stories about brothers transformed into birds and wondrous children. Its folkloric origins are indicated by fairy tale motifs and a structure characteristic of the classical fairy tale. The mention of magical objects (in particular, gold chains) is characteristic of both types of fairy tales, but they perform different functions: they serve as a means of transforming children into birds and as a marker of the miraculous nature of the characters. This article examines literary versions that have largely preserved archaic features: the Old French poem “Elioxe”, which has come down to us in 13th-century manuscripts and represents the typologically earliest source, and one of the tales from “Dolopathos”, first included by the creator of the Latin version, Johannes de Alta Silva. The transformation of folklore motifs is associated with a change in the roles of gold chains, as well as the emergence of new functions that form associative rather than semantic links.