(well,) wash my mouth out with soap
A sarcastic exclamation of mock regret over a statement someone else found or might find offensive, objectionable, or tasteless. A: "You could at least watch your language around my kids!" B: "Oh, I'm sorry, is it too harsh for their sensitive little ears? Well, wash my mouth out with soap." Are you upset? Am I being too mean? I guess I ought to wash my mouth out with soap, huh?
Well, wash my mouth out with soapand WWMMOWS
sent. & comp. abb. a request indicating pretend remorse for saying something profane or objectionable. So you don’t like my advanced vocabulary. WWMMOWS.