achilles--tendon
A*chil"les' ten"don, n. Etym: [L. Achillis tendo.] (Anat.) Defn: The strong tendon formed of the united tendons of the large muscles in the calf of the leg, an inserted into the bone of the heel; -- so called from the mythological account of Achilles being held by the heel when dipped in the River Styx.