mis ‧ no ‧ mer /mɪsˈnəʊmə $ -ˈnoʊmər/ BrE AmE noun [countable]
[ Date: 1400-1500 ; Language: Old French ; Origin: mesnommer 'to name wrongly' ]
a wrong or unsuitable name:
‘Silent movie’ is a misnomer since the movies usually had a musical accompaniment.