Substitute-User or Super-User ?

[Guy Harris]

>> Was it originally meant to be become-superuser command ?
>
>It's because the default operation of su, as you mention, is to become
>root, who is the super user.

And because, as I remember, the V6 version *only* let you become
super-user; it didn't take an optional "who should I become" argument. 
Back then, it *was* the "super user" command; I guess when they added
the user-name argument, they came up with "substitute user" as the best,
well, umm, what *is* the name for a phrase formed from an acronym? :-)

(Remember, the etymology of UNIX commands is, at times, quirky. 
Consider V6's "dsw" command - no, it's not "Department of Sanitary
Waste", nor is it roughly based on "Do Svidanja".)