"Idiom" and "idiocy" share a common cognate, you know.

Nathan and Z are walking around the Riverside yard, picking up fallen twigs, putting them in the red wheelbarrow. 

Nathan: This tree drops so many branches every time there's a storm.

Z [in his own world again]: WHAT?

Nathan: I said, this tree drops so many branches every time there's a storm.

Z [furiously at work]: You don't need to tell me twice.