Main Page | See live article | Alphabetical index A hatter is a maker or seller of hats. The proverbial expression "mad as a hatter" may refer to the mercury-poisoning suffered by many hatters in the eighteenth and nineteenth centuries, when mercury was used in the manufacture of felt. See also: The Hatter in Alice's Adventures in Wonderland External Links "Mad as a Hatter" at Urban Legends Questions & Answers: Mad as a Hatter This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.