Mad Hatter Day

The phrase "mad as a hatter" was around long before Carroll started writing. Colloquially used to describe an eccentric person, the phrase originated in the 19th century, back when mercury was used to manufacture felt hats. The hatters who visited these factories often developed mercury poisoning (referred to then as the hatters' shakes), which could lead to slurred speech, memory loss, tremors, and excessive timidity.

The real Mad Hatter was probably a man named Theophilus Carter. Lewis Carroll never referred to the character as the Mad Hatter. In both Alice's Adventures in Wonderland and Through the Looking-Glass, Carroll only refers to him as the Hatter—or Hatta.