“Mad as a hatter” is an English phrase meaning “crazy” and although its origin is unclear, it actually has nothing to do with Lewis Carroll’s memorable character from “Alice’s Adventures in Wonderland”.
There are at least two theories on the origin of this phrase:
- 1. The most widely accepted theory proposes the saying comes from hat-making as mercury was regularly used in the trade and resulted in mercury poisoning developed by the hatters.
- 2. The second theory suggests that the phrase may actually be a corruption of an earlier phrase “mad as an adder”, meaning “mad as a viper”.
Whatever the case may be, it seems that madness and hatters came into the English language (almost) hand in hand – Oxford English Dictionary cites the earliest mention of the word hatter is in 1389, while the word mad first appeared 10 years later, in 1399.