lay on, Macduff

Go ahead and give it your best shot. Macduff, a character in Shakespeare's Macbeth, correctly suspected Macbeth of murdering King Duncan. After Macbeth murders Macduff's family, Macduff leads an army against Macbeth. Their final confrontation includes Macbeth's challenging line: “Lay on, Macduff; / And damned be him that first cries, ‘Hold, enough!'” People who wanted to show off their erudition and wit simultaneously used the phrase in any “Go ahead!” context until it became through overuse a very tired cliche′ to which the best response is “Who's Leon Macduff?”