MEDICAL NAME FOR YOUR BUTT
'Butt' actually comes from the official medical term for you bum, buttocks.
Butt cheeks are each comprised of two big muscles - the gluteus maximus and gluteus minimus. For this reason, doctors will also refer to your bum as your 'glutes'.
The hole in the middle of your glutes is medically called the anus.
The buttocks serves three important roles in humans: the fat layer padding serves to make sitting comfortable, the large gluteus muscles provide a large contribution to your propulsion during walking, and it is the end of the digestive conduit.