اندر (Classical Persian) comes from Middle Persian 𐭡𐭩𐭭, from Old Persian 𐎠𐎫𐎼, from Proto-Iranian *Hántarah, from Proto-Indo-Iranian Hántaras, from Proto-Indo-European h₁énteros, from Proto-Indo-European -teros — Contrastive or oppositional adjectival suffix.