"abnormal accumulation of fat on the buttocks of certain races," 1822, Modern Latin, from steato- "fat, tallow," comb. form of Greek stear (genitive steatos) "solid fat, suet" (see stearin) + Greek pyge "rump, buttocks" + abstract noun ending -ia. Related: Steatopygous "having enormously fat buttocks" [Century Dictionary]; steatopygy.