bug#1381: 23.0.60; capitalization of car and cdr in the doc

[Drew Adams]

>     OK, that's one thing. But my question was whether these 
>     shouldn't simply be treated as normal Emacs terms - just
>     like cons, buffer, symbol, and frame, after
>     they have been introduced (defined).
> 
> The reason for using @sc on car and cdr is that they are acronyms.
> Those other terms are not acronyms.

I see. That makes sense, I guess, though I'm not sure it's important. (If we
always stuck to that convention, then we might always write "EMACS" or "EMacS",
not "Emacs". ;-))

FWIW, this is what Wikipedia says about the orthography of acronyms:

 The most common capitalization scheme seen with acronyms
 and initialisms is all-uppercase (all-caps), except for
 those few that have linguistically taken on an identity
 as regular words, with the acronymous etymology of the
 words fading into the background of common knowledge, such
 as has occurred with the words scuba, laser, and radar.

That's the argument I'd make here: "car" and "cdr" have linguistically taken on
an identity as regular words. The machine registers that were at the orgins of
these terms are incidental to the current meanings, and knowledge of that
historical relation is anecdotal.

I see "cdr" (for Lispians) the same way I see "radar". We should encourage
thinking of these as common terms, rather than as acronyms about machine
registers. Rather than facilitating understanding, I think it gets in the way of
understanding (and readability) to write "RADAR" and "CDR".