英语词源字典 - 在线词源网站

cancer (n.): Old English cancer "spreading sore, cancer" (also canceradl), from Latin cancer "a crab," later, "malignant tumor," from Greek karkinos, which, like the Modern English word, has three meanings: crab, tumor, and the zodiac constellation (late Old English), from PIE root *qarq- "to be hard" (like the shell of a crab); cognates: Sanskrit karkatah "crab," karkarah "hard;" and perhaps cognate with PIE root *qar-tu- "hard, strong," source of English hard.

Greek physicians Hippocrates and Galen, among others, noted similarity of crabs to some tumors with swollen veins. Meaning "person born under the zodiac sign of Cancer" is from 1894. The sun being in Cancer at the summer solstice, the constellation had association in Latin writers with the south and with summer heat. Cancer stick "cigarette" is from 1959.
canker (n.): 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.
carcinoma (n.): "malignant tumor," 1721, from Latin carcinoma, from Greek karkinoma "a cancer," from karkinos "cancer," literally "crab" (see cancer) + -oma.