Changeling

A changeling, also historically referred to as an auf or oaf, is a human-like creature found throughout much of European folklore. According to folklore, a changeling was a substitute left by a supernatural being when kidnapping a human being. Sometimes the changeling was a "stock" (a piece of wood made magically to resemble the kidnapped human), more often the changeling was a supernatural being made magically to look like the kidnapped human.

Supernatural beings blamed for stealing children included fairies, demons, trolls, nereids and many others. Usually, the kidnapped human was a child; but there were cases, particularly in Scandinavia and Ireland, where adults were taken.

Some modern scholars have argued these stories of replaced children originated as folklore explanations for autism or other developmental conditions.