Here are some fun hat facts from The Encyclopedia of Trivia
Probably the first real hat was the broad-brimmed petasos of the ancient Greeks. It was worn only for traveling, as a protection against the weather. A chin strap held the petasos on or allowed it to hang down the back when not needed.
The wearing of hats was made compulsory on Sundays and holidays in early seventeenth century Britain, in order to preserve the livelihood of the country's 8,000 hat makers.
Abraham Lincoln kept his important documents inside his hat.
Tipping the hat comes from the military salute, which in turn comes from men in armor lifting the visor to show their faces.
A ten-gallon hat actually holds a little less than one gallon.
London black cabs are designed to be tall enough for a gentleman to sit in without the need to remove his top hat.