European folklore has the myth of changelings. People used to believe that fairies or trolls would steal human babies and leave a changeling in their place—usually a sickly or naughty fairy child. To check if a baby was a changeling, they’d do weird things, like putting the baby on a hot shovel (thinking the changeling would jump off) or leaving it alone with porridge and a knife to make it reveal itself. This myth was often used to explain why some children suddenly got sick or acted differently.

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