As Mad as a Hatter
The term as mad as a hatter is quite famous, and also fairly appropriate as Tim Burtons take on Alice in Wonderland has recently come out. But did you know that Hatters probably were indeed mad.
Hatters worked with mercury in the manufacture of hats, mercury is a nasty substance that can cause many diseases such as acrodinia,Hunter-Russell syndrome and minamata desease. A few signs and symptoms of mercury poisoning are:
paresthesia or “pins and needles”/limb gone to sleep
Skin discolouration and shedding
Persistant faster-than-normal heart rate and high blood pressure
profuse sweating and increased salavation
Phrases also has this to say;
All in all not the kinda thing you want when trying to impress a date, and does go some way to explaining where the term came from. However. There is one more theory.
Hatters was a term given to miners that worked alone in New Zealand. Often going mad from the solitude.