dwm: Don’t care what the D stands for, but there are a bunch of X11 window managers ending in ‘wm’ so that’s probably what this is too.

dmenu: Since it’s coming from the same place as dwm, it’s probably a menu app that goes well with it.

st isn’t obvious, I agree, but it makes sense to give a short name to the program you use most frequently.

The origin of the name are clear, but the name itself should describe what is it because these name can be find out of context.

These names can't be easily understandood without context. And these name will be found without context: For exemple, you may meet this name in a process list. In this case you don't understand why the process "dwm" is eating a lot of gpu power.

A variable name can be short, because it's name will be found in it's context.

Is that a convention, or just what they stand for? (Do the window manager and the menu suck, because they don't have the "s" prefix? Is st static because it doesn't have the "d" prefix? Why do we abbreviate "terminal" but not "menu" / why not follow the established abbreviation of "term" as in xterm, dtterm, eterm, etc.? How come the "s" prefix in sprop and sselp stands for "simple" instead of "suckless"?)