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.
Suckless tools are meant for hardcore *nix hackers who already know how to look up this information, so no, the naming doesn't really matter. Anyone who knows how to use the ps command will also know the man command, so if someone wants to know what that dwm process is, they can just do "man dwm".
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.