What is the origin of this phrase? Nobody knows.

Posted by Boyd DuPree on December 15, 1999

"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"?