Achilles tendon

the tendon joining the calf muscles to the heel bone.
Contemporary Examples

A second doctor suggested it might be possible to extend his Achilles tendon.
The Fall and Rise of Skateboarder Danny Renaud Michael Daly August 20, 2013

Historical Examples

Achilles tendon, the great tendon of the heel, where Achilles was vulnerable.
The Nuttall Encyclopaedia Edited by Rev. James Wood

Make the Achilles tendon in same way and leave back of thigh off to be stuffed.
Taxidermy Leon Luther Pray

noun
the fibrous cord that connects the muscles of the calf to the heelbone

from Modern Latin tendo Achillis, first used by German surgeon Heister and so-called in reference to the one vulnerable spot of the great Greek hero Achilles, whose mother held him by the heel when she dipped him in the River Styx to render him invulnerable (though this story is not in Homer and not found before 1c. C.E.). Earlier Achilles’ sinew, from Modern Latin chorda Achillis, coined 1693 by Dutch anatomist Philip Verheyden when dissecting his own amputated leg. Hence figurative use of heel of Achillies for “vulnerable spot” (1810).

Achilles tendon n.
The large tendon connecting the heel bone to the calf muscle of the leg. Also called calcanean tendon, heel tendon.
Achilles tendon [(uh-kil-eez)]

A tendon connecting the heel bone with the calf muscle of the leg.

Note: In Greek legend, the hero Achilles could be wounded only in the heel.