Patients with cataracts often describe their vision as “foggy” or “like looking through a frosted window”. The term “cataract” is derived from the Latin, “cataracta” which means “waterfall” and the Greek” katarhaktes” which means “waterfall, broken water; swooping, rushing down”.
In Latin, cataracta had the alternate meaning “portcullis“ and it is possible that the name passed through French to form the English meaning “eye disease” (early 15c.), on the notion of “obstruction”. Early Persian physicians called the term nazul-i-ah, or “descent of the water”—vulgarised into waterfall disease or cataract—believing such blindness to be caused by an outpouring of corrupt humour into the eye (Wikipedia)