Government of Canada
Symbol of the Government of Canada

Flesh out vs. flush out

Question:

Is it flush out or flesh out the details? Is there a history behind the saying?

Answer:

Both are correct English idioms, but in the context you give, the correct phrase is flesh out the details, not flush out.

The Canadian Oxford Dictionary defines flesh out as "make or become substantial" and flush out as "force or drive (a person) out of a hiding place, etc." Common Errors in English Usage (2003) clearly states the difference between these expressions:

To "flesh out" an idea is to give it substance, as a sculptor adds clay flesh to a skeletal armature. To "flush out" a criminal is to drive him or her out into the open. The latter term is derived from bird-hunting, in which one flushes out a covey of quail. If you are trying to develop something further, use "flesh"; but if you are trying to reveal something hitherto concealed, use "flush."