Where did the name coffin bone originate?

The horse's coffin bone is located in each hoof of the animal. The hard tissue of the hoof encases the bone; thus called the coffin bone.

Skulls and hooves are sometimes found in the burial places of the Indo-European people of the Copper Ages to the Middle Ages. These people found the horse very spiritual-like and had many rituals dealing with them including burying the hooves with the remains of a person.