and Etymonline.com gave this:

cancer
O.E., from L. "a crab," later, "malignant tumor." Greek physician Galen, among others, noted similarity of crabs to some tumors with swollen veins. From Gk. karkinos, which, like the Mod.E. word, has three meanings: crab, tumor, and the zodiac constellation (1391), from PIE base *qarq- "to be hard" (like the shell of a crab); cf. Skt. karkatah "crab," karkarah "hard;" and probably cognate with PIE base *qar-tu- "hard, strong," source of Eng. hard. Meaning "person born under the zodiac sign of Cancer" is from 1894. Cancer stick "cigarette" is from 1959.


formerly known as etaoin...