In Greek mythology, Achilles was the
son of an immortal goddess named Thetis and a mortal man named
Peleus. When Achilles was born, Thetis thought she could make
him immortal by submerging him into the River Styx. The legend
says Thetis held Achilles by his heel when she dipped him into
the river. Therefore, his heel was not touched by the magical
waters of the River and it remained mortal and thus vulnerable.
Achilles went on to become a hero in the Trojan War, but was
killed toward the end of the war when he was shot in the heel by
an arrow.
Since then, the term
"Achilles' heel" has come to mean a vulnerability or weakness in
an otherwise strong person. For example, a fighter might be
brought down by his Achilles' heel, such as pride, or
overconfidence.
The Achilles tendon is
the largest and strongest tendon in the body, stretching from
the calf muscles down to the heel. It is strong, but prone to
injury. Doctors speculate this is because of its limited blood
supply and the fact that it frequently has high tension placed
upon it, especially during walking and running.