This is a Phyrgian cap. I'm surprised I only just learned about its symbolism.
It once symbolized freedom. This association comes from Roman times. It was even banned around the French revolution.
It might have adorned the statue on top of the U.S. Capitol, except that Jefferson Davis objected. The cap did make it on to the seals of the U.S. Senate and the state of Iowa. It also figures on the coat of arms of various South American countries.
I think its interesting... and cute.