In Swedish folklore, changelings (bortbytingar) were human children believed to have been swapped by supernatural beings — gnomes, trolls or fairies — for their own offspring. The belief arose as an explanation for congenital disabilities, autism or developmental conditions that could not be explained medically. Parents sometimes performed brutal tests to force the changeling to reveal itself. The belief was particularly widespread in the Nordic countries from the Middle Ages to the 19th century.
In some areas the changeling would be exposed by cooking soup in an eggshell — a sight so strange that the supernatural creature would lose composure and give itself away
