The butt is the end of something, and buttock is the diminutive of butt, it is the end of the torso and where the lower limb begins; to the anatomist it is the gluteal region. The gluteal muscles, which form the bulk of the buttocks in the slim subject, stabilise the hip and make upright bipedal walking possible. But the buttocks are a target area for fat deposition, varying in racial characteristic, so some are termed steatopygenous by their proclivity to get outsize buttocks in relation to the rest of the body’s structure.
Gluteus maximus is attached proximally and medially to the back of the pelvis, its thick coarse fibers pass laterally and downwards to insert in part into the back of the femur, but mostly into the ilio-tibial tract which descends down the outside of the thigh to attach to lower femur and upper tibia. Gluteus medius and minimus hidden beneath maximus, do not contribute to the size of the buttock.
Not unlike the breast, the buttock is an object of concupiscence, some like them small and neat, others like them large. So, like the breast, this creates a field for the surgeon, to make larger or smaller the buttocks of the presenting patient, of either sex (or sometimes in process of changing sex), in the range of procedures known as gluteoplasty. Although this might in some instances be a corrective procedure for the effects of an injury, in others it is an esthetic procedure which may augment the buttocks by a prosthesis inserted beneath the muscles, or reshape the buttocks by liposculpture, to the desired appearance.