The phrase (as) mad as a hatter means completely insane.
All of its early uses are associated with Ireland. The earliest instance that I have found is from The Belfast Commercial Chronicle (Ireland) of 18th June 1827:
The fees upon the elevation of Lord Norbury, amount, it appears, to about 1,500l, which his Lordship must pay, and consequently, as the vulgar say, “he is as mad as a hatter.”
It is then recorded in Noctes Ambrosianæ. N° XLIV., published in Blackwood’s Edinburgh Magazine of June 1829 (Odoherty is an Irish name):
– North: Many years—I was Sultan of Bello for a long period, until dethroned by an act of the grossest injustice; but I intend to expose the traitorous conspirators to the indignation of an outraged world.
– Tickler (aside to Shepherd): He’s raving.
– Shepherd (to Tickler): Dementit.
– Odoherty (to both): Mad as a hatter. Hand me a segar.
Another early occurrence of the phrase is found in Legends and Stories of Ireland (London, 1834), by the Irish author Samuel Lover (1797-1868). A story titled The Sheebeen House contains the following:
“Oh it’s only me, and it’s time for me to go, you know yourself, Terry,” said the deserter—“and the wife will be as mad as a hatter if I stay out longer.”
The phrase also appeared in a poem published in The Evening Packet, and Correspondent (Dublin) of 29th April 1834.
The Morning Post (London) of 3rd February 1835 reported that during a trial, the phrase was used by “a man named Driscol, an emerald “gem” of the first water”.
The phrase also appeared in The Dublin Evening Post of 7th March 1835, with the following remark:
Why hatters are said to be madder than other Gentlemen, we know not.
It has often been said that the phrase alludes to the effects of mercury poisoning sometimes formerly suffered by hat-makers as a result of the use of mercurous nitrate in the manufacture of felt hats.
But I have doubts as to the validity of this explanation, because neither the contexts in which the early instances of (as) mad as a hatter appear nor the persons who in the 19th century tried to make sense of the phrase associated it with the manufacture of hats, let alone with mercury poisoning. If the phrase did originally refer to the hat makers’ disease, some of the contemporaries would certainly have noticed the connexion.
Furthermore, in the 19th century, the word hatter was used in several other similes expressing notions different from that of insanity: drunk as a hatter, to work like a hatter, to lie like a hatter, to go at like a hatter, to do it like a hatter, and, perhaps, to hit like a hatter.
The following explanation of (as) mad as a hatter given by the editor of The Framlingham Weekly News (Suffolk) of 16th January 1864 is open to question, but what is interesting is that he relates it to two other phrases and associates it with no disease whatsoever:
In the palmy days of the high-priced beavers, hatters earned good wages and were invariably drunk and noisy all the forepart of the week, working like slaves during the last days. Hence came the phrases, “Mad as a hatter,” “Works like a hatter,” and “Drunk as a hatter.”
The Brighton Guardian (Sussex) of 10th April 1861 contains yet a different expression:
Why it should be so, probably no one can tell, but in modern slang hatters have been declared to enjoy an unenviable preeminence in the art of lying, and to “lie like a hatter” is considered the very acme of mendacity.
A different phrase appeared in The Times (London) of 10th February 1849, which reported that during “a pugilistic contest”, a person acting as one combatant’s second in the fight
urged him on with the expression, “Go in at him like a — hatter.”
Likewise, The Durham Chronicle (County Durham) of 7th January 1853 published a letter in which a correspondent explained that, had a certain person found a way of solving a particular problem,
he wad o’ gane [= would have gone] at it like a hatter.
This notion of intensity is expressed in a different expression, appearing in The Inverness Courier (Scotland) of 15th July 1852:
A hatter’s cleverness has very nearly become a proverb. To “do it like a hatter” is to say a thing shall be done at once, in hot haste, cleverly, neatly—in short, in every way as it should be done, but as nobody else could do it.
The following probably shows a pun on an existing phrase to hit like a hatter; it is from The Tipperary Vindicator, and Limerick Reporter (Ireland) of 20th November 1866, which reported that at a trial a witness had declared, about the defendant, that a woman
raised her hand, hit him on the hat like a hatter (a laugh) but I don’t know if she is a hatter (renewed laughter).
Apart from the occurrence in The Times of London, the intensive phrases to go at like a hatter, to do it like a hatter and (if it did exist) to hit like a hatter appear in Northern-English, Scottish and Irish newspapers. This might be related to the intensive expression like a hatter, chiefly used in Scotland, meaning with the utmost energy or vigour, with might and main, “like mad”.
Among the Scottish authors who used like a hatter were:
– James Stewart (died 1843), in Sketches of Scottish Character, and other poems (Perth, 1857):
“Lat’s a’ be tip’ce to weet the whissle
[= tuppence to wet the whistle]
O’ Wiggie Willie.”
At this my mouth began to water,
I birl’d my tip’ce too like a hatter.
[= I clubbed my tuppence too like a hatter.]
– Janet Hamilton (1795-1873), in Our Local Scenery, from Poems of Purpose (Glasgow, 1865):
Ye maun rin like a hatter,
Bring up twa pails fu’ o’ clear caller water.
[You must run like a hatter,
Bring up two pails full of clear fresh water.]
– Robert Ford (1846-1905), in Thistledown: a book of Scotch humour, character, folk-lore, story & anecdote (Paisley, 1891):
Here Crummy lies, enclosed in wood,
Full six feet one and better,
When tyrant Death grim o’er him stood,
He faced him like a hatter.
In my opinion therefore, (as) mad as a hatter merely represents a specialised usage, originally Irish, of the intensive expression like a hatter.
I also think that the latter is related to hatter, a variant of the Scottish and Northern-English verb hotter, meaning:
– to move in an uneven, jerky manner, as a vehicle on a rough road, to walk unsteadily, to totter
– of liquid, etc.: to seethe, bubble, boil steadily, hence, of a person, to tremble with impatience, excitement, anger, etc.
Interestingly, this verb gave rise to an expression rather similar to (as) mad as a hatter, which was hottering mad. In Hard Times (1854), set in the fictitious Northern-English mill town of Coketown, the English novelist Charles Dickens (1812-70) makes Stephen Blackpool say of his co-worker Rachael, whom he wishes to marry:
But for her, I should ha’ gone hottering mad.
One of the equivalent French phrases is travailler du chapeau, literally to work from the hat. The word chapeau is metonymic for tête, head, that is to say, the chapeau, which covers the head, is substituted for the latter, as in the English phrase to have a bee in one’s bonnet.
The phrase (as) mad as a hatter and Alice’s Adventures in Wonderland:
In Alice’s Adventures in Wonderland (1865), by Lewis Carroll (Charles Lutwidge Dodgson – 1832-98), both the March Hare and the Hatter are characters associated with madness: the Cheshire Cat refers to them as “both mad”—although he adds “we’re all mad here”—and this is reinforced by the fact that the March Hare attends the tea party that the Hatter gives.
The phrase (as) mad as a March hare is one of the sources of the March Hare, while (as) mad as a hatter is likely to be among the origins of the Hatter—whom, however, the author never calls the Mad Hatter.