Merriam-Webster Collegiate Dictionary - carbuncle

 noun  Etymology: Middle English, from Anglo-French charbucle, carbuncule, from Latin carbunculus small coal, ~, diminutive of carbon-, carbo charcoal, ember  Date: 13th century  1.  a. obsolete any of several red precious stones  b. the garnet cut cabochon  2. a painful local purulent inflammation of the skin and deeper tissues with multiple openings for the discharge of pus and usually necrosis and sloughing of dead tissue  • ~d adjective  • carbuncular adjective