Erethism

Erethism is an abnormally high degree of irritability or sensitivity to stimulation of an organ or body part; abnormal excitement of a bodily organ or tissue

Erethism or erethism mercurialis is a symptom complex of mercury poisoning, presenting with excessive shyness, timidity and social phobia. This was common among hat makers of old England who used mercury to stabilize the wool in a process called felting. Hence the creation of the Mad Hatter by Lewis Carrol in the Alice stories.