Merriam-Webster's Collegiate® Dictionary, 11th Edition
CANKER
I. noun
Etymology: Middle English, from Anglo-French cancre, chancre, from Latin cancer crab, cancer Date: before 12th century
1. a. an erosive or spreading sore, an area of necrosis in a plant, any of various disorders of animals marked by chronic inflammatory changes, a caterpillar destructive to plants, rust 1, a source of corruption or debasement, dog rose , cankerous adjective
II. verb (cankered; cankering)
Date: 14th century
transitive verb to infect with a spreading sore, to corrupt the spirit of, intransitive verb to become infested with canker, to become corrupted