Nomenclature
The oldest-known written record of the tendon being named for Achilles is in 1693 by the Flemish/Dutch anatomist Philip Verheyen. In his widely used text Corporis Humani Anatomia, Chapter XV, page 328, he described the tendon's location and said that it was commonly called "the cord of Achilles", now also called "tendo achillies" by anatomists. ("quae vulgo dicitur chorda Achillis")
The name Achilles' heel comes from Greek mythology. Achilles' mother, the goddess Thetis, received a prophecy of her son's death. Hearing this, she dipped him into the River Styx to protect his body from harm. However, she kept hold of his heel, meaning that the water did not touch this part of his body and it was therefore vulnerable. During the Trojan War, Achilles was struck on his unprotected heel by a poisoned arrow shot by Paris, which killed him. In the same war, Achilles is also said to have cut behind Hector's Achilles tendons, having killed him, and threaded leather thongs through the incisions in order to drag him behind a chariot.
The Achilles tendon is also known as the calcaneal tendon. Because eponyms, names relating to people, have no relationship to the subject matter, most anatomical eponyms also have scientifically descriptive terms. The term calcaneal comes from the Latin calcaneum, meaning heel.
Read more about this topic: Achilles Tendon