A number of Iron Age bracteates from Scandinavia have long been thought to depict a version of the Norse myth about the death of the god Baldr. In two versions of the myth, as it is preserved in literary sources, Baldr is said to be invulnerable to everything except for one special or highly unlikely weapon. In the best-known rendition, this is the mistletoe. Despite efforts to avoid it, this improbable weapon ends up causing his death.

It is a fate that Baldr may be said to share with the Greek hero Achilles about whose invulnerability two stories have come down to us. In one, his mother Thetis attempts to secure immortality for her infant son by anointing him with ambrosia and purifying him in the embers of the hearth, but Peleus, the child's father, interferes and so the treatment remains incomplete. In another, better known, version, Thetis is said to have dipped her son in the waters of Styx and this has made his body invulnerable, except for his heel where she held him. Like Baldr, who is killed with the unusual weapon, Achilles dies when a wound is inflicted on his heel, and this part of his body has become a proverbial reference to a seemingly small, but crucial, weakness. These two mythological figures have little else in common, but Achilles’ heel is nonetheless relevant in the present context – proverbially and also in a more concrete sense.