The New Dictionary of Cultural Literacy, Third Edition. 2002.
malapropism
(MAL-uh-prop-iz-uhm) A humorous confusion of words that sound vaguely similar, as in We have just ended our physical year instead of We have just ended our fiscal year.
Mrs. Malaprop, a character in an eighteenth-century British comedy, The Rivals, by Richard Brinsley Sheridan, constantly confuses words. Malapropisms are named after her.