Fran says that "porkeau de pruneau" is French for "pork and prune" when, translated to French, "pork and prune" is actually "porc et pruneau". However, this is incorrectly regarded as a goof: the audience knows that Fran has no higher education and doesn't speak French. This is an obvious character joke and Fran was merely being facetious, poking fun at the fact that she may not be upper-crust and speak French, like those in the snobbish circles she's engaged in, but she can fake it and sound just as pretentious as they do.