The Curse of the Long Fingernails
One of the most scary and terrifying myths from the middle ages is the curse of the dead fingernails. Originally called “The Dead Fingernail”, it tells the story of a woman who is possessed by demons, and in turn grows the fingernails of the dead. These stories were probably made to explain the phenomenon of incredibly long fingernails, which can happen from time to time. Take this woman for example, this is Ayanna Williams from the U.S.. Williams was able to grow such long fingernails, that she won the world record for long fingernails, at 10.09 ft!

This is another example of a fantastic ability of the human body that would probably have inspired urban legends and terrifying stories in the past.