cataracts

PIE word
*ḱóm
From Late Middle English cataractes, cataractis, cateractes, used to translate καταρράκται (katarrháktai, “(probably) floodgates, sluices”) in the Septuagint and cataractae (“floodgates, sluices”) in the Vulgate versions of the Bible. The Middle English words are plural forms of cataract, cataracta, cateract, cateracte (“floodgate of heaven”), from Old French cataracte (modern French cataracte), and from its etymon Latin cataracta (“floodgate; waterfall”), from Ancient Greek καταρ(ρ)άκτης (katar(rh)áktēs, “(noun) waterfall; (adjective) rushing downwards”), from καταρ(ρ)ᾱ́σσω (katar(rh)ā́ssō, “to pour down; to rush downwards”) + -της (-tēs, suffix forming nouns denoting a state of being). Καταρ(ρ)ᾱ́σσω (Katar(rh)ā́ssō) is derived either:
* from κᾰτᾰ- (kătă-, prefix meaning ‘downwards’) + ἀρᾰ́σσω (arắssō, “to dash to pieces; to strike”) (further etymology unknown, possibly onomatopoeic) or ῥᾱ́σσω (rhā́ssō, “to dash; to strike”) (possibly ultimately from Proto-Indo-European *wreh₂ǵʰ- (“to pound, strike”)); or
* from καταρρηγνύναι (katarrhēgnúnai, “to break down”).
By surface analysis, cataract + -s (suffix forming pluralia tantum).