'Achilles' originates from Ancient Greek, specifically the word 'Ἀχιλλεύς' (Akhilleus), where 'ἄχος' (akhos) meant 'pain' or 'grief'.

'Ἀχιλλεύς' transformed into the Latin word 'Achilles', and eventually became the modern English word 'Achilles'.

Initially, it referred to the Greek hero, but over time it evolved into a metaphor for a point of vulnerability.