<Li> Roger Crab, a 17th - century hermit who, after working for a short time as a hatter, gave all his goods to the poor and wore homemade sackcloth clothes . Although this was presaged by political and religious radicalism, and was followed by a long married life . </Li> <Li> An adaptation of the Anglo - Saxon word atter meaning poison, closely related to the word adder for the poisonous Crossed Viper . Lexicographers William and Mary Morris in Morris Dictionary of Word and Phrase Origins (1977) favour this derivation because "mad as a hatter" was known before hat making was a recognized trade . According to A Dictionary of Common Fallacies (1980), "' mad' meant' venomous' and' hatter' is a corruption of' adder', or viper, so that the phrase' mad as an atter' originally meant' as venomous as a viper' ." </Li> <Li> Historical significance: Abraham Lincoln was shot by John Wilkes Booth, and Booth was shot by Boston Corbett . Corbett spent his early life as a hat maker, and it is believed that the effects of his early life job affected his decision - making for his future . He was considered "mad as a hatter" for going against orders when he had Booth cornered in a barn in Virginia, and shooting Booth instead of taking him alive . After investigation, Corbett was forgiven for his disobedience, but left the army and went back to hat making . After a few years, Corbett was even more mad than people had once thought, and he was thrown into an insane asylum . Incidentally, Corbett managed to escape, and he was never seen again . </Li> <P> In a section of the January--June 1829 issue of Blackwood's Edinburgh Magazine, headed Noctes Ambrocianæ . No . XL1V, there is a conversation between a group of fictional characters: </P>

Where did the term mad as a hatter come from