/ ˈmæləprɒpɪzəm; NAmE -prɑːp-/ noun
an amusing mistake sb makes when they use a word which sounds similar to the word they wanted to use, but means sth different
ORIGIN: From Mrs Malaprop, a character in Richard Brinsley Sheridan's play The Rivals , who confuses words like this all the time.
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WORD ORIGIN
mid 19th cent.: from the name of the character Mrs Malaprop in Sheridan's play The Rivals (1775) + -ism .