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”.