Whup-ass

Saturday evening, after I had gone well beyond the call of professional or financial duty to a particular client, the client's brother-in-law indicated he would "open a can of whup-ass" on me if I didn't move my car immediately.

For future reference, if anyone should happen to receive a similar threat from this individual, his "can of whup-ass" is of the one-calorie, caffiene- and sugar-free, watching-your-figure diet variety with just a hint of lemon zest.