Interesting Word - Malapropism

A malapropism is the "inappropriate" use of a word. It is derived from the French phrase mal à propos (literally "ill-suited").

(It's also called a Dogberryism or acyrologia. Basically if you substitute an incorrect word for a word with a similar sound, you've made a malapropism, for example: "I resemble that remark", instead of "I resent that remark". If you want to see it in action, just read Sheridan's 1775 play 'The Rivals', and in particular the character Mrs. Malaprop.)