late Old English cancer "spreading ulcer, cancerous tumor," from Latin cancer "malignant tumor," literally "crab" (see cancer); influenced in Middle English by Old North French cancre "canker, sore, abscess" (Old French chancre, Modern French chancre). The word was the common one for "cancer" until c.1700. Also used since 15c. of caterpillars and insect larvae that eat plant buds and leaves. As a verb from late 14c. Related: Cankered; cankerous. Canker blossom is recorded from 1580s.