1911 Encyclopædia Britannica/Changeling
CHANGELING, the term used of a child substituted or changed for another, especially in the case of substitutions popularly supposed to be through fairy agency. There was formerly a widespread superstition that infants were sometimes stolen from their cradles by the fairies. Any specially peevish or weakly baby was regarded as a changeling, the word coming at last to be almost synonymous with imbecility. It was thought that the elves could only effect the exchange before christening, and in the highlands of Scotland babies were strictly watched till then. Strype states that in his time midwives had to take an oath binding themselves to be no party to the theft or exchange of babies. The belief is referred to by Shakespeare, Spenser and other authors. Pennant, writing in 1796, says: “In this very century a poor cottager, who lived near the spot, had a child who grew uncommonly peevish; the parents attributed this to the fairies and imagined it was a changeling. They took the child, put it in a cradle, and left it all night beneath the “Fairy Oak” in hopes that the tylwydd têg or fairy family would restore their own before morning. When morning came they found the child perfectly quiet, so went away with it, quite confirmed in their belief” (Tour in Scotland, 1796, p. 257).
See W. Wirt Sikes, British Goblins (1880).