canker

Canker is commonly known as the name for a type of spreading sore that eats into the tissue—a use that obviously furnished the verb with both its medical and figurative senses. The word ultimately traces back to Latin cancer, which can refer to a crab or a malignant tumor. The Greeks have a similar word, karkinos, and according to the ancient Greek physician Galen, the tumor got its name from the way the swollen veins surrounding the affected part resembled a crab's limbs. Cancer was adopted into Old English, becoming canker in Middle English and eventually shifting in meaning to become a general term for ulcerations. Cancer itself was reintroduced to English later, first as a zodiacal word and then as a medical term.