Traditionally derived from a Proto-Indo-European *h₁égʰi- with cognates including Sanskrit अहि (áhi), Avestan 𐬀𐬲𐬌 (aži) and Old Armenian իժ (iž). However, the letter chi (χ) is expected to derive from a palatal consonant (ǵ) and so these terms are now generally connected with ὄφις (ophis), leaving the origins of ἔχις a mystery. Some now consider this a taboo corruption of Proto-Indo-European *h₁ógʷʰi-, *h₁égʷʰi-.
- (5th BC Attic): IPA: /ékʰis/
- (1st BC Egyptian): IPA: /ɛ́kʰis/
- (4th AD Koine): IPA: /éxis/
- (10th AD Byzantine): IPA: /éçis/
- (15th AD Constantinopolitan): IPA: /éçis/
- ἔχιδνα (ekhidna)