Flesh/flush out.

Meat and bleat.

Dear Word Detective: I work in a PR agency where we have to come up with a lot of new ideas for our clients to keep paying us money. So we have a lot of brainstorms. And out of the brainstorms come a lot of ideas that we all need to go back to our desks and “flush out.” I have been working with the same person for ten years and we always argue about this, because I tell her we need to “flesh out” the ideas, not “flush them out.” Perhaps in the brainstorm, I can grant her, we are “flushing out” the ideas from deep within out brains (like flushing out a drain or a flock of geese from the woods), but the subsequent beefing up of these bare-bones ideas should be referred to as “fleshing them out.” Who is right? — Brad Kuerbis.

Whoa. You folks have been arguing about this for ten years? Sounds like you need to hire yourselves to brainstorm a new bone of contention. Your conciliatory attempt to parse “flush out” as akin to running a Roto-Rooter on one’s noggin is laudable, although it does imply that the deepest levels of our brains are clogged with marketing strategies. But the truth is simply that you are right and she is wrong.

The meaning of “to flush” when it first appeared as a verb in English around 1300 was “to fly up suddenly,” as a covey of quail will upon being startled in a field by hunters and their dogs. The transitive form of the verb, meaning “to drive into the open,” appeared around 1450, and the “sudden movement of liquid” sense appeared in the 16th century. “Flush” is thought to be echoic, imitating the sound of sudden flight, and both the “force out” and “water” senses may also be related to the word “flash.”

“Flesh” is, of course, what menus call “meat,” and the first use of “flesh” as a verb in the 16th century was to mean “reward a hawk or hound with part of the game killed as encouragement.” A wide range of meanings subsequently developed, including, in the 17th century, “to clothe a skeleton with flesh.” As a hobby this was apparently a non-starter, as most uses have been figurative with the sense of “to fill out, to make a rudimentary framework more substantial” (much as you use “beef up” in your question, “beef” having served as a synonym for both “strength” and “substance” since the 19th century). The process you describe of building substance on the foundation of an inspired idea thus clearly calls for “flesh out.”