The Collaborative International Dictionary of English v.0.48:

Misnomer \Mis*no"mer\, v. t.
   To misname. [R.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Misnomer \Mis*no"mer\, n. [OF. pref. mes- amiss, wrong (L. minus
   less) + F. nommer to name, L. nominare, fr. nomen name. See
   Name.]
   The misnaming of a person in a legal instrument, as in a
   complaint or indictment; any misnaming of a person or thing;
   a wrong or inapplicable name or title.
   [1913 Webster]

         Many of the changes, by a great misnomer, called
         parliamentary "reforms".                 --Burke.
   [1913 Webster]

         The word "synonym" is fact a misnomer.   --Whately.
   [1913 Webster]

WordNet (r) 3.0 (2006):

misnomer
    n 1: an incorrect or unsuitable name