“THERE is a place. Like no place on Earth. A land full of wonder, mystery, and danger! Some say to survive it: You need to be as mad as a hatter.” - Hatter (Alice in Wonderland, 2010)
Lewis Carroll’s Alice’s Adventures in Wonderland famously features an eccentric character who was popularly called the Mad Hatter.
The phrase “mad as a hatter,” used to describe someone who’s crazy or prone to unpredictable behavior, seems very likely referring to this character.
Or does it?
Verdict:
FALSE
While Lewis Carroll’s Mad Hatter (and later cartoon and live-action adaptations) helped cement the phrase “mad as a hatter” in popular culture, they did not originate it.
The real story is quite much darker.
In the 18th and 19th centuries, hatters commonly used a toxic substance, mercuric nitrate, as part of the process of turning the fur of small animals into felt for hats.
Yes, you read right!
It's part of a process called "carroting". In order to make felt, which is what many hats are made of, the hatters had to get the fur of a beaver or rabbit to stick together in a mat of thick, stiff fabric. To get the fur off the skin cleanly, mercuric nitrate was used.
In those times, since workplace safety standards were often lax, hat makers and clothing manufacturers, who had prolonged exposure to mercury, developed a variety of physical and mental ailments, including tremors (dubbed “hatter’s shakes”), speech problems, emotional instability and hallucinations.
Sound like a scene out of a horror film? It probably looked it too. Hat-making used to be a hazardous hobby disguised as a profession.
The harmful effects of mercury weren’t clearly recognised until about the 1950s.
Historical records also suggest that Sir Isaac Newton, Blaise Pascal, and several other well-known scientists experienced mercury poisoning.
Still, even today, chronic mercury poisoning is sometimes called Mad Hatter’s Disease. Thanks to better diagnoses and more rigorous public health and occupational safety standards, the disease in its extreme form is rare.
So, while the character didn’t invent the phrase; he became its most famous walking advertisement.
References:
https://www.history.com/articles/where-did-the-phrase-mad-as-a-hatter-come-from
https://australianballet.com.au/blog/mad-as-a-hatter?
https://www.discovermagazine.com/how-poisonous-chemicals-created-the-phrase-mad-hatter-44205
