Question

Where did the expression mad as a hatter come from?

Answer 1

"Mad as a hatter" is a colloquial English phrase used in conversation to suggest that a person is suffering from insanity. It is believed to have its origins in the North of England where men predominantly worked in the hattery business which used mercury in the hat making process.

The mercury caused Erethism, also known as erethism mercurialis or mad hatter syndrome which is a neurological disorder that affects the whole central nervous system, as well as a symptom complex derived from mercury poisoning.