Misnomer
Misnomer , noun
[Old French pref. mes- amiss, wrong (Latin minus less) + French nommer to name, Latin nominare, from 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.
Many of the changes, by a great misnomer, called parliamentary “reforms”.
The word “synonym” is fact a misnomer.
Misnomer , transitive verb
To misname. [Rare]