In ancient Egypt, the heart was the key to a happy afterlife. It lived on after death, they believed, and in the Duat, the Netherworld, it revealed a truth man's words could not hide.
The 42 gathered gods would measure the heart and if it weighed more than the Feather of Truth which adorned the head of Maat, their Goddess of Justice, Order, and Truth, it was consumed by the Goddess Ammit, Devourer of the Dead, who had the body of a crocodile, a lion, and a hippopotamus, and you were gone from existence forever.
People had a lot of ways to get heavy hearts. Theft, anger, even eavesdropping
added weight.