NIL

NIL /nil/  No.  Used in reply to a question, particularly
   one asked using the `-P' convention.  Most hackers assume this
   derives simply from LISP terminology for `false' (see also
   {T}), but NIL as a negative reply was well-established among
   radio hams decades before the advent of LISP.  The historical
   connection between early hackerdom and the ham radio world was
   strong enough that this may have been an influence.