We put hats in boxes, but the inverse is often true, too. Hats evoke a sense of place and time—they conceal the head, but they also reveal something about the wearer. A Stetson suggests a rugged lifestyle, just as a cloche conjures the image of a Roaring Twenties flapper. An Australian book I recently edited described a character in a “flat cap,” and based on context I knew this was a contemptible sartorial choice, but I couldn’t picture the hat without Google’s help. (Apparently they’re called driving caps in the United States.) I started to wonder, What other headwear don’t I know about?