malapropism
n. a linguistic error in which one word is mistakenly used for another having a similar sound, often to ludicrous effect, as in She was wearing a cream casserole (for camisole) or I can’t eat pasta without marzipan (for parmesan). The term is named for Mrs. Malaprop, a character in Richard Brinsley Sheridan’s play The Rivals (1775), whose speech is full of preposterous errors of this kind.