mad as a hatter


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mad as a hatter

- Refers to the fact that hat makers suffered mental illness in the old days when they got mercury poisoning from treating fur.
See also related terms for mad.

mad as a hatter

Completely insane; from the former use of mercury in processing furs or hides to make hats. Hatters absorbed large amounts of this over the years which gradually poisoned them, often leading to mental disturbance.
References in classic literature ?
"He must be as mad as a hatter," exclaimed the Colonel.
The hat makers, called hatters, became ill and went crazy, thus the term "mad as a hatter." That's because this element is a lethal neurotoxin (poison to the central nervous system) when it loses two electrons (negatively charged particles).
A There are little mysteries, little clues in the book that I found fascinating like him saying: "I'm investigating things that begin with the letter M." That was huge for me because, when you do a little digging, you realise you're talking about a hatter and there's this term "mad as a hatter".