As dull as dishwater

As dull as ditchwater / As dumb as ditchwater / What a bore! / Bore to death


Non sapere di niente

Non sapere né di me né di te / Non sapere né di pepe né di sale / Non sapere neanche di acqua calda / Non sapere neanche di acqua bollita / Essere stupidi come l'acqua calda


Meanings
Fig.: said of someone or something showing nothing interesting. To be extremely dull and tedious

Examples
She's beautiful but as dull as dishwater, and you can tell as soon as she opens her mouth
È una ragazza bellissima, ma non sa di niente e te ne accorgi non appena apre la bocca

That much-publicized and hailed book to me is dull as ditchwater. You read it with difficulty and slowly get to the end of it to ask yourself, "So what?"
Quel libro tanto pubblicizzato e osannato per me non sa assolutamente di niente. Lo leggi a fatica e lentamente arrivi alla fine per chiederti: “E allora?”

Origin
It seems that the dishwater of this expression, alluding to the grayish water in which soiled dishes are soaked, came to be in the first half of the 20th century as a mispronunciation of the original phrase As dull as ditchwater, which referred to the muddy water of roadside ditches