A term of unknown origin, most probably translated or inherited from another language into Ancient Greek. The only PIE explanation is an unsupported hypothesis: the PIE word *hekʷ-peds (“painful (lit. sharp) foot”) evolved into Illyrian [script needed] (*āk̂ú-pedios) > *ākhúpdeos > *akhiddeùs and then, via a Pre-Greek source, the -dd- shifted to -ll-. The meaning "painful foot" refers to his vulnerability but it has been erroneously translated as "swift footed" because of the similarity with the root *ōk̂ú-s (“quick”) from whence a similar latin term acupedius comes from
- (5th BC Attic): IPA: /akʰil̚le͜ʊ́s/
- (1st BC Egyptian): IPA: /akʰil̚lɛ́ʍs/
- (4th AD Koine): IPA: /axil̚léɸs/
- (10th AD Byzantine): IPA: /açil̚léps/
- (15th AD Constantinopolitan): IPA: /açiléps/
- Ἀχίλλειος (Akhílleios)
- p. 999 in S. C. Woodhouse’s English-Greek Dictionary: A Vocabulary of the Attic Language. Routledge & Kegan Paul Limited. 1950.