This English idiom is very well known although is not used in day-to-day life. This recognition is perhaps down to Lewis Carroll’s novel Alice in Wonderland in which we find a character with the name The Mad Hatter.
The expression is used to express that someone is mad. Generally speaking it is used to denote the extreme of madness and that someone is not just mad but is in fact verging on craziness.
The earliest printed usage of the phrase can be found in Blackwood’s Edinburgh Magazine from the year 1829. It can be found in a conversation and reads;
TICKLER (aside to SHEPHERD.): He’s raving.
SHEPHERD (to TICKLER.): Dementit.
ODOHERTY (to both.): Mad as a hatter. Hand me a segar.
After this the expression quickly gained popularity and can be found in a number of works; mainly from British writers and novelists. It is suggested that the idea behind the expression is the fact that in the past hats were manufactured using mercury which was a material which caused damage to the nervous system and thus those who made hats developed a reaction to this and acted as though they were “mad.”
The most famous example of this expression is found in Lewis Carroll’s novel Alice in Wonderland. One of the main characters is named The Mad Hatter and thus the phrase is used frequently throughout. An example of this can be found in the following citation; “in that direction,’ the Cat said, ‘lives a hatter: and in that direction, lives a March Hare. Visit either you like: they’re both mad.”