This is a large tendon found in the back of the heel that attaches the large group of gastroc soleus muscles of the calf to the heel bone, or calcaneus. The achilles tendon is named after Achilles, the Greek mythological hero. Legend has it that his mother Thetis dipped her son into the river Styx holding onto her baby’s heel, rendering him invulnerable everywhere except at the back of the ankles, the body part that she held out of the river.