dull as dishwater Flat, boring.

This expression began life in the eigh- teenth century as dull as ditchwater, alluding to the muddy color of the water in roadside gullies. “He’d be sharper than a serpent’s tooth, if he wasn’t as dull as ditchwater,” says Dickens’s Fanny Cleaver (Oliver Twist). This version survived on both sides of the Atlantic well into the twentieth century. Either through careless pronunciation or through similar analogy it occasionally became dishwater—water in which dishes had been washed and which consequently was dingy and grayish.