steatopygia n.

glycerine of stearic acid, white crystalline compound found in animal and vegetable fats (it was derived from mutton fat, among other things), 1817, from French stéarine, coined by French chemist Marie-Eugène Chevreul (1786-1889) from Greek stear (genitive steatos) "tallow, stiff fat, suet" (contrasted with pimele "soft fat, lard;" compare Latin sebum/adeps), possibly from PIE *stai- "stone," also "to thicken, stiffen" (see stone (n.)). Stearic (1831) is from French stéarique.

word-forming element in names of countries, diseases, and flowers, from Latin and Greek -ia, noun ending, in Greek especially used in forming abstract nouns (typically of feminine gender); see -a (1). The classical suffix in its usual evolution (via French -ie) comes to Modern English as -y (as in familia/family, also -logy, -graphy). Compare -cy.

In paraphernalia, Mammalia, regalia, etc. it represents Latin or Greek -a (see -a (2)), plural suffix of nouns in -ium (Latin) or -ion (Greek), with formative or euphonic -i-.