carbuncle
noun·/ˈkɑːr.bʌŋ.kəl/
1. A painful, inflamed cluster of boils, an angry knot of infection under the skin (medical). A carbuncle is deep, hot, and serious.
The fever began as a carbuncle on his shoulder, a small fire the body couldn’t easily put out.
2. A deep red gemstone, especially a garnet, described in older writing as if it held a coal-like inner glow (historical).
In the lamplight the carbuncle looked alive, a red that seemed to remember flame.
Etymology
From Latin carbunculus “little coal,” diminutive of carbo “coal.” The metaphor split into two lives: the disease named for its fiery inflammation, and the stone named for its ember-red shine.
Related Words
furunclea boil; often contrasted with carbuncle
garnetthe gemstone sense most commonly implied
inflammationthe physiological core
carbuncularpertaining to a carbuncle