Steatopygia

steatopygia \ˌstē-a-tə-ˈpi-j(ē-)ə, -ˈpī-\ noun: an excessive development of fat on the buttocks

Etymology: New Latin, from steat-, stear + Greek pygē buttocks

Just brainstorming, I guess stereopygia would be “the property of having solid buttocks.” And who would possess stereopygia? Athletes, I reckon.