/ ˌmɪsˈnəʊmə(r); NAmE -ˈnoʊ-/ noun
a name or a word that is not appropriate or accurate :
'Villa' was something of a misnomer ; the place was no more than an old farmhouse.
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WORD ORIGIN
late Middle English : from Anglo-Norman French , from the Old French verb mesnommer , from mes- wrongly + nommer to name (based on Latin nomen name).