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-).
1650s, "cold, icy," from French glacial or directly from Latin glacialis "icy, frozen, full of ice," from glacies "ice," probably from a suffixed form of PIE root *gel- "cold; to freeze" (source also of Latin gelu "frost"). Geological sense "pertaining to glaciers" apparently was coined in 1846 by British naturalist Edward Forbes (1815-1854). Hence figurative sense "at an extremely slow rate," as of the advance of glaciers. Related: Glacially.
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<a href="https://www.etymonline.com/word/post-glacial">Etymology of post-glacial by etymonline</a>
Harper, D. (n.d.). Etymology of post-glacial. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/post-glacial