Why 'Stops' for exposure?

And its converse, "stopping up the light".
Or should that be "going up the light"?

Well, the usual converse of "stopping down" is "opening up". But all that goes to show is that conventional or colloquial terminology can be quite a world of its own, and not entirely obvious.

And I keep seeing expressions like "use a higher aperture" or something like that. Which is entirely meaningless. An aperture is a hole, like a window. Moving the window up, down, or from side to side doesn't change its size.

Regards,
Peter