CATARACT: A large waterfall; a medical condition of the eye.
So how did this word end up with two completely different meanings?
It originated with the Greek word kataraktes, meaning something that is rushing or swooping down which is a derivative of katarassein, from kata– “down” plus arassein “strike. There are several words whose first element comes from kata–, including cataclysm, catapult, catalepsy, catalogue and catastrophe.
The Greek word applied to a number of things that rush down, including a swooping bird and a waterfall. It was transferred into Latin in the form cataracta and in that language could refer to a waterfall, a flood-gate or a portcullis (the vertical grated gate to a castle which could be dropped to bar entrance).
But than from about the middle of the sixteenth century, cataract also began to be applied to the medical condition in which the lens of the eye goes progressively opaque. It seems that doctors were using the word as a simile for something that stopped light entering the eye. An older expression for the same condition was web in the eye, so the name was most likely derived from the barred structure of the portcullis or window grating, rather than as a physical barrier. It sounds improbable, but nobody seems to have come up with a better explanation.
http://www.worldwidewords.org/weirdwords/ww-cat1.htm
Bookmarks