The expression or comment "Brain Freeze" means that the roof of your mouth is getting so cold that its affecting some of the nerves in your brain making it feel like a brain freeze.
Due to the laws of motion the airbag causes force in the other direction while the person is moving forward, thus trying to equal out the force acting apon the person to make them stay in place.
Drinking alcohol slows down brain functioning, neural activity, and further reduces the functioning of various vital functions in the body.
