epigastrium n.

before vowels reduced to ep-, before aspirated vowels eph-, word-forming element meaning "on, upon, above," also "in addition to; toward, among," from Greek epi "upon, at, close upon (in space or time), on the occasion of, in addition," also "after," from PIE *epi, *opi "near, at, against" (source also of Sanskrit api "also, besides;" Avestan aipi "also, to, toward;" Armenian ev "also, and;" Latin ob "toward, against, in the way of;" Oscan op, Greek opi- "behind;" Hittite appizzis "younger;" Lithuanian ap- "about, near;" Old Church Slavonic ob "on"). A productive prefix in Greek; also used in modern scientific compounds (such as epicenter).

1650s, from Modern Latin gastricus, from Greek gaster (genitive gastros) "stomach, paunch, belly," often figurative of gluttony or greed, also "womb, uterus; sausage," by dissimilation from *graster, literally "eater, devourer," from gran "to gnaw, eat," from PIE root *gras- "to devour" (source also of Greek grastis "green fodder," Latin gramen "fodder, grass," Old English cærse "cress").