The Collaborative International Dictionary of English v.0.48:

Rupia \Ru"pi*a\, n. [NL., fr. G. ? filth, dirt.] (Med.)
   An eruption upon the skin, consisting of vesicles with
   inflamed base and filled with serous, purulent, or bloody
   fluid, which dries up, forming a blackish crust.
   [1913 Webster]