The term ''Iran'' derives directly from Middle Persian , first attested in a third-century inscription at Naqsh-e Rostam, with the accompanying Parthian inscription using the term , in reference to the Iranians. The Middle Iranian ''ērān'' and ''aryān'' are oblique plural forms of gentilic nouns ''ēr-'' (Middle Persian) and ''ary-'' (Parthian), both deriving from Proto-Iranian language ''*arya-'' (meaning "Aryan", i.e. "of the Iranians"), recognized as a derivative of Proto-Indo-European language '''', meaning "one who assembles (skilfully)". In the Iranian languages, the gentilic is attested as a self-identifier, included in ancient inscriptions and the literature of the Avesta, and remains also in other Iranian ethnic names ''Alan'' ( ) and ''Iron'' (). According to the Iranian mythology, the country's name comes from the name of Iraj, a legendary prince and shah who was killed by his brothers.