Source : Free On-Line Dictionary of Computing

M-expression LISP
     
        (MLISP) The original "{meta-language}" {syntax} of {Lisp},
        designed by {John McCarthy} in 1962.  MLISP was intended for
        external use in place of the parenthesised {S-expression}
        {syntax}.
     
        ["LISP 1.5 Programmer's Manual", J. McCarthy et al, MIT Press
        1962].
     
        (1994-11-22)