word-forming element meaning "after," from Latin post "behind, after, afterward," from *pos-ti (source also of Arcadian pos, Doric poti "toward, to, near, close by;" Old Church Slavonic po "behind, after," pozdu "late;" Lithuanian pas "at, by"), from PIE *apo- (source also of Greek apo "from," Latin ab "away from" see apo-).
"pertaining to a flood" (especially The Flood of Genesis), 1650s, from Late Latin diluvialis, from Latin diluvium "flood, inundation," from diluere "wash away," from dis- "away" (see dis-) + -luere, combining form of lavere "to wash" (from PIE root *leue- "to wash"). Related: Diluvian.
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<a href="https://www.etymonline.com/word/postdiluvial">Etymology of postdiluvial by etymonline</a>
Harper, D. (n.d.). Etymology of postdiluvial. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/postdiluvial