I followed a reference in that article to the article on Letter Case [0] which just blew my mind:
> The terms upper case and lower case […] originated from the common layouts of the shallow drawers called type cases used to hold the movable type for letterpress printing. Traditionally, the capital letters were stored in a separate shallow tray or "case" that was located above the case that held the small letters.
I can’t believe I’d never considered the origin of “case” in uppercase and lowercase might be an actual physical “case”.
It's similar to being "out of sorts", which today (and maybe even historically) means you're not feeling well. It came from letterpress where the case of type is collectively called a "sort" and if you were trying to put together a print run and you ran out of, say, the letter 'r', you are now "out of sorts".
> During typesetting, individual sorts are picked from a type case with the right hand, and set into a composing stick held in the left hand from left to right, and as viewed by the setter upside down. As seen in the photo of the composing stick, a lower case 'q' looks like a 'd', a lower case 'b' looks like a 'p', a lower case 'p' looks like a 'b' and a lower case 'd' looks like a 'q'. This is reputed to be the origin of the expression "mind your p's and q's". It might just as easily have been "mind your b's and d's".
> The terms upper case and lower case […] originated from the common layouts of the shallow drawers called type cases used to hold the movable type for letterpress printing. Traditionally, the capital letters were stored in a separate shallow tray or "case" that was located above the case that held the small letters.
I can’t believe I’d never considered the origin of “case” in uppercase and lowercase might be an actual physical “case”.
[0]: https://en.wikipedia.org/wiki/Letter_case#Terminology