Cache is pronounced like cash, which the $ symbol is supposed to allude to.

Wow, how have I never put 2 and 2 together on that.

You're not alone - it took me way longer than it should have done to figure that one out!

leading to the unfortunate abbreviation sometimes drawn on blackboards, "$hit"

It is an apt abbreviation if you visualize shit tightly packed in a container. And when you thrash the cache, shit hit the fan (and spills to VRAM.)

Yes, they are obviously caches. I just didn’t understand your comment.