Topic summary
Hatter
Extracted from the Wikipedia article Hatmaking.
"Mad" hatters
In 18th- and 19th-century England, mercury was used in the production of felt, which was commonly used in the hat-making trade at the time. Long-term use of mercury products often resulted in mercury poisoning-induced erethism among hat-makers. This is sometimes claimed to be the origin of the phrase "mad as a hatter".