>    Could different chars have been used than
>    c, a, d, and r?  Of course.  The c and r
>    aren't needed, and we could have used f for
>    first and r for rest, or h for head and
>    t for tails, or | for car and . for cdr, or
>    - for car and @ for cdr:
> 
>     cadaar  =  frff  =  hthh  =  |.||  =  -@--
>     caar    =  ff    =  hh    =  ||    =  --
>     caaar   =  fff   =  hhh   =  |||   =  ---
>     caddar  =  frrf  =  htth  =  |..|  =  -@@-
> 
>     cdadar  =  rfrf  =  thth  =  .|.|  =  @-@-
>     cdddar  =  rrrf  =  ttth  =  ...|  =  @@@-
>     caddr   =  frr   =  htt   =  |..   =  -@@
> 
> How do you pronounce frff? .|.|? or @@@-?
> 
> One thing that car, cadr, cdr, cdar .. have going for them is that
> they are (semi-)words, with pronounciation rules.  No clue how to
> pronounce -some-do-hickey-@-$-> ...  which is immensly useful when
> explaning thing, it is much easier to say kə.ˈdɑɹ (CDAR) of a list
> then 'the rest of the first' .. or whatever it would become.

;-)

Yes.