"lower belly," 1680s, from Modern Latin hypogastrium, from Greek hypogastrion, from hypo "under, below" (see hypo-) + gaster (genitive gastros) "belly, paunch; womb" (see gastric). Related: Hypogastric (1650s).
word-forming element meaning "under, beneath; less, less than" (in chemistry, indicating a lesser oxidation), from Greek hypo (prep. and adverb) "under, beneath; up from under; toward and under (i.e. into)," from PIE root *upo "under."
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").