Achilles (a mythological Greek warrior – said to be the bravest hero in the Trojan war) was dipped in the magical river Styx as an infant by his mother, Thetis, in an attempt to make him immortal. She held him by the heel so this part of his anatomy did not receive the immortal protections conferred on the rest of his body. (Sadly she forgot to re dip the still dry heel). This left him vulnerable to injury to his “Achilles’ heel”. Eventually he was wounded in battle by an arrow in the heel and died soon afterwards.

Now we have a saying; we speak of a person’s “Achilles’ heel” as the weakest point of their personality or a product’s “Achilles’ heel” as vulnerability to failure because of a weak link in supporting structures.