Problems with 'null' symbol

'||
NIL
':||
;;; An error occurred in function CREATE-SYMBOL-FROM-CHARS:
;;; Error: Invalid symbol--no characters after package marker

'user::||
;;; An error occurred in function CREATE-SYMBOL-FROM-CHARS:
;;; Error: Invalid symbol--no characters after package marker

(describe '||)
;;; Autoloading C:\PROGRAM FILES\CORMAN TECHNOLOGIES\CORMAN LISP 
2.01\sys\describe.lisp ...
SYMBOL:
     name:           NIL
     value:          NIL
     package:        #<PACKAGE "COMMON-LISP">
     property list:  (COMMON-LISP::TYPE-DISCRIMINATOR #< COMPILED-FUNCTION: 
#x192EEB0 >)
     function:       #< UNBOUND >
     function type:  NIL
     constant:       T
     special:        NIL
     jump table:     0
     variable table: 0
     heap address:   #x1710000
(setq x '||)
NIL
(symbol-name x)
"NIL"
(symbol-name nil)
"NIL"

;;;; Allegro:

 > '||
||
 > 'user::||
 >
COMMON-LISP-USER::||
 >

 > (describe '||)
|| is a SYMBOL.
   It is unbound.
   It is INTERNAL in the COMMON-GRAPHICS-USER package.

 > (setq x '||)
||
 > (symbol-name x)
""