Thinking cap

"Put on your thinking cap"

What is a thinking cap? Was it something someone once tried to invent - perhaps some sci-fi gadget with an electro-magnetic field that when placed on ones head was supposed to accelerate brainwaves beyond their capacity? - or was it just an idea made up to persuade school kids to push the envelope in their"thinking"?

help.

I thought it was a kiddie show expression -- the TV hostess telling the children to put on their thinking caps. But the Morris Dictionary of Word and Phrase Origins says: "thinking cap. The expression 'put on your thinking cap,' meaning 'give careful and thoughtful consideration to this,' comes from the practice of judges in olden times of putting on a cap before sentencing a criminal. The practice is still followed in some countries, though not in the United States, when the death sentence is to be announced."