The coffin-bone, also known as the distal phalanx or third phalanx, is an essential part of the hoof in horses. It connects the hoof wall to the interior of the hoof, and it's critical for the horse's soundness and comfort. There are a few synonyms for the coffin bone, including pedal bone, P3 bone, and third phalanx bone. These terms are often used interchangeably in veterinary and farrier circles. It's important to note that if a horse experiences any trauma or damage to the coffin bone, it can result in severe lameness and permanent damage. Therefore, proper hoof care and regular veterinary check-ups are crucial for maintaining a horse's health and well-being.