carbuncle

Concise Oxford English Dictionary © 2008 Oxford University Press:
carbuncle /ˈkɑːbʌŋk(ə)l/

▶noun

• 1 a severe abscess or multiple boil in the skin.

• 2 a bright red gem, in particular a cabochon garnet.

– derivatives
carbuncular adjective.

– origin ME: from OFr. charbuncle, from L. carbunculus ‘small coal’, from carbo ‘coal, charcoal’.