Carcinus

The Latin or Greek name for a crab, or in mythology, a large crab sent by the goddess Hera to attack Heracles during his battle with the Hydra.

From Greek 'karkinos' (crab). In Greek mythology, Carcinus was the specific name of the giant crab, and the term became the root for many medical words because ancient physicians associated the appearance of spreading cancers with a crab's legs.