Source : Webster's Revised Unabridged Dictionary (1913)

Erethism \Er"e*thism\, n. [Gr. ? irritation, fr. ? to stir,
   rouse, fr. ? to stir: cf. F. ['e]r['e]thisme.] (Med.)
   A morbid degree of excitement or irritation in an organ.
   --Hoblyn.

Source : WordNet®

erethism
     n : an abnormally high degree of irritability or sensitivity or
         excitability