Beginning in the 17th century, people liked to prefix "mar-" to nouns to create a term for someone who mars, or spoils, something. A mar-joy was bad enough, but even worse was a mar-all. Although today the word "plot" often carries an implication of secrecy or ill intent, the "plot" used in the formation of "marplot" simply meant "a plan for the accomplishment of something." A marplot, therefore, can really mess up a perfectly good thing. The word may not have been invented by English playwright Susannah Centlivre, but it first surfaces in print in her 1709 play The Busy Body. That title refers to a character named Marplot, who misguidedly gets in the way of the lovers in the play.