What does this doc-string say to the novice lisp programmer? It says
"We're telling you that the function called \"cdr\" actually returns the
abstract \"cdr\" of a lisp object, just in case that isn't obvious." It
goes on, implicitly by omission, to say "if you really don't know what a
cdr is by this stage, you're so stupid that there's no point in us
bothering to tell you."
...
I suggest making this doc-string more helpful by appending the following
to it:
"Loosely speaking, the cdr of LIST is LIST without its first element."