Webster's unabridged dictionary (Third Edition) defines a malapropism as "a usually humorous misapplication of a word or phrase; specifically, a blundering use of a word that sounds somewhat like the one intended but is ludicrously wrong in the context." The term is derived from Mrs. Malaprop, a lady in Richard Sheridan's 1775 comedy, "The Rivals," noted for her misuse of words.
Greenblatt, M. H.
"Mrs. Malaprop, The Ad(Wo)Man,"
Word Ways: Vol. 5
, Article 13.
Available at: http://digitalcommons.butler.edu/wordways/vol5/iss1/13