Having cold feet is an expression whose meaning has come to be associated with fear or a lack of confidence to face a certain situation, say performing in public, or asking the boss for a raise.
Achilles was a mythological demigod whose demise came in the form of an arrow that struck him squarely in his heel.
People demand a lot from their feet, which are tasked with taking hundreds to thousands of strides every day, running long distances, and traveling up and down hills and stairs.
