misnomer
n. countablen. a name that is wrong or misleading because it does not describe the thing correctly. You use this when something is called by a name that makes it sound different from what it really is.
n. a name that is incorrect or misleading in its application to a person or thing. Often used to describe a title or label that fails to accurately represent the subject's nature or function.
Calling the small dog a 'beagle' is a misnomer.
The term 'blue moon' is a misnomer because the moon does not actually appear blue during this event.
While the term 'cold war' is widely accepted in historical discourse, some scholars argue it is a misnomer, as the period was marked by several proxy conflicts and significant military spending.
The noun is derived from Late Middle English misnoumer (“(law) mistaken identification of a person; plea based on such misidentification”), from Anglo-Norman mesnomer, a noun use of Anglo-Norman mesnomer, mesnommer, and Old French mesnomer, mesnommer (“to name incorrectly”), from mes- (prefix meaning ‘badly, wrongly’) + nomer, nommer (“to name”) (from Latin nōmināre, the present active infinitive of nōminō (“to name”), from nōmen (“name”) (from Proto-Indo-European *h₁nómn̥ (“name”)) + -ō (suffix forming regular first-conjugation verbs)). The verb is derived from the noun.