Hand dyed with indigo in Kojima, the heel of one of each pair of socks is gripped tightly during dyeing, blocking the indigo and showing the undyed fabric underneath.

In Ancient Greek myth, the goddess Thetis dipped her baby Achilles into the waters of the magical river Styx, which divided the worlds of the living and the dead, to make him invulnerable. Achilles grew up to be a great warrior who was protected in battle by the magic of the water. He was eventually killed by Paris who shot him in the heel with an arrow. The heel was the place where his mother had gripped him as a baby, and was the only part not to be touched by the water.