The Progressive Era. During the period known as the Progressive Era (1890s to about 1920) the U.S. government became increasingly activist in both domestic and foreign policy.
One possible link between brain freeze and other headaches is local changes in brain blood flow. If further research confirms all these types of headaches are caused by blood flow changes, new drugs that block widening of the blood vessels - called vasodilation - could improve treatment for sufferers.
We actually still do not really know the physiological cause of the brain freeze. That's the true explanation. We know what triggers it, but we don't know the nitty gritty of it. Only thing we can be sure of is that if you want to avoid it, don't eat your ice cream too fast, or suck down your Slurpee too fast.