'cataractous' originates from Late Latin, specifically the word 'cataracta', where the Greek element 'kata-' (via Latin) meant 'down' and the root referred to a 'rushing or falling' (as in a waterfall).

'cataractous' changed from the Latin word 'cataracta' which entered English via Middle English as 'cataract' (originally meaning 'waterfall'); the adjective was later formed by adding the suffix '-ous' to produce 'cataractous'.

Initially it meant 'waterfall' (the Greek/Latin sense of a down-rushing of water), but over time the term was applied to a film or flow over the eye and evolved into the medical sense 'opacity of the lens' and the adjective meaning 'affected by cataracts'.