It's happened to the best of us.
There's a saying that you've been using for as long as you can remember. Then one day, someone informs you, hopefully kindly, that you've actually been saying it wrong this whole time.
Former users of "take it for granite" and "pre-Madonna" know what we're talking about.
A listener named Elizabeth told us she was in a meeting at work when someone said, "We still need to flush out this concept more." Elizabeth says everyone knew what the person meant, but she thinks "flesh out" would be more correct in this case.
The confusion over "flesh" and "flush" made vol. 2 of Merriam Webster's list of top 10 commonly confused words. If you say these two words out loud, it's easy to hear why these two get confused -- without careful pronounciation, "flesh" and "flush" sound almost identical. The fact that these two words can be used in similar contexts doesn't help.
To "flesh out" something means to put meat on its bones. Metaphorically, it means to add details or make something more complete. You might meet with your co-workers to flesh out a proposal that you're working on together.
To "flush out" something can mean a couple of different things. One meaning is the "cleaning out the system" meaning -- you know, like flushing a toilet. Another meaning is to bring something out into the open. You might flush out birds from a tree or, if you're lucky, you might flush out Big Foot from wherever he happens to be hiding.
"Flush out" can also be used metaphorically. If you want to know why someone did something, you might try to flush out their reasoning or bring it out into the open. This meaning is perhaps the source of the confusion between "flesh out" and "flush out."
Is there a phrase you thought you were saying correctly only to discover that you've actually been saying it wrong your whole life?