Of disputed origin. One theory is that it is from Elamite 𒁹𒆪𒊏𒀾 (mku-ra-aš2 /kuraš/, “shepherd, bestowed care, protector”); earliest cuneiform attestations of the name, even instances prior to the founder of the Achaemenid Empire, always end in /-aš/ opposed to /-uš/ an unexplainable development for Akkadian and Elamite phonologically if the original was the Iranian /-uš/. This has suggested rather that the later more well-known Iranian version is in fact the adaptation, perhaps brought on by the fact that Old Persian "a" stems never have a final /-š/ but "u" stems do in the nominative.
𐎤𐎢𐎽𐎢𐏁 (ku-u-ru-u-š /Kuruš/)
- Persian: کوروش (Kuroš)
- → Ancient Greek: Κῦρος (Kûros) (see there for further descendants)
- → Classical Syriac: ܟܘܪܫ (Kūreš)
- Old Armenian: քորէշ (kʿorēš)
Tavernier, Jan (2007) Iranica in the Achaemenid Period (ca. 550-330 B.C.): Linguistic Study of Old Iranian Proper Names and Loanwords, Attested in Non-Iranian Texts, Peeters Publishers, →ISBN