C17: via French from Latin, from Greek kataklusmos deluge, from katakluzein to flood, from kluzein to wash
Word Origin and History for cataclysm
n.
1630s, from French cataclysme (16c.), from Latin cataclysmos or directly from Greek kataklysmos "deluge, flood, inundation," from kataklyzein "to deluge," from kata "down" (see cata-) + klyzein "to wash," from PIE *kleue- "to wash, clean" (see cloaca).