Cancer was first documented by the Ancient Egyptians over 3500 years ago. It wasn't given its modern name until 400 BCE, though, when the Ancient Greek physician Hippocrates noticed that many tumors with swollen veins are shaped like crabs, so he named the mass of cells karkinos, which meant "crab". This became cancer in Latin, which was later borrowed into English. This crabby connection is also why Cancer is the zodiac of the crab. Now let's go back to karkinos. Through the Proto-Italic word kankos, this comes from an even earlier Proto-Italic word, karkros, which meant "enclosure" (in reference to the shape a crab's pincers form). That in turn may be reconstructed to the Proto-Indo-European root krkr, which meant "circular". Usage of the word cancer in literature over time, both for the symbol and the disease, has been markedly increasing since the 1970s.
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd