Definition from Wiktionary, the free dictionary
Literally: whichever pot is not boiling, pickup that pot
- If a pot of water is not boiling, it does not make any (high-pitched) sound. This means figuratively that the pot of water is defective. If one deliberately picks up such a pot, then it figuratively means that one is deliberately publicizing somebody else's weaknesses or secrets.
- to air somebody's dirty laundry
- to blurt out somebody's weakness
- to let somebody's skeletons out of the closet