Anyone who has studied Western languages has come across the expression "false friends." These are words that resemble English ones but don't have the same meaning. For example, those who have studied French know that le coin isn't something you receive in change; it's the corner. Spanish speakers know you wouldn't want to wash your hands with sopa.
But one need not look outside the bounds of English for such mix-ups. Malapropismsthe mistaken use of a word in place of a similar-sounding onecan be hilarious. Benny Hill and Soupy Sales nearly made careers out of funny malapropisms. For the rest of us, however, malapropisms can either be funny ... or they might confuse other people.
One such confusable is flesh and flush. Nobody would ever say, "Flesh the toilet," but it's not uncommon to hear someone say they want to "flush out an idea" when they really mean to "flesh out an idea."
To flesh out means "to make more detailed." Imagine making a scarecrow or marionette. You'd start with a frame of stickslike a skeletonthen you'd add stuffing, clothes, facial features and so on to make it more real. It would quite literally flesh out the puppet. The same goes for an idea. We might start with something that's bare bones, but then think it through until it's got some meat to itflesh it out.
Flush out can mean "to clean something by passing water through it." There's the obvious example of a toilet, which gets flushed. You can also flush out a car radiator, for example.
Flush out also means "to force out into the open" or "drive from a place of concealment." It makes me think of the hedge behind my house. Every time I walk past it, any finches and rabbits that are in the hedge scurry away. It's not my intention, but each time I walk past the hedge, I flush out all the little creatures (although they appear to be getting used to me now).
Perhaps it could also be said that we've just flushed out a pair of false friends.
Sources: Oxford Dictionary of Current English.
Music from this Episode: "In the Flesh" by Blondie; "Yakety Sax" by Boots Randolph; "Flushed from the Bathroom of Your Heart" by Johnny Cash.