What's the matter? Cat got your tongue?

Do you know the expression, 'Has the cat got your tongue?'

This is said when someone is expected to say something and doesn't.

My question is, why so they have to say something if they don't want to? If they have nothing to say why do they have to pollute the air with banal chatter?

So, the next time someone says to you. "what's the matter? Has the cat got your tongue?" Say yes it has and watch the person who says that squirm. They won't know what to say and where to look and you can carry on with your silence.