Iran
The term Iran derives directly from Middle Persian Eran, first attested in a 3rd-century inscription at Rustam Relief, with the accompanying Parthian inscription using the term Aryan, in reference to Iranians. The Middle Iranian eran and aryan are oblique plural forms of gentilic er- (Middle Persian) and ary- (Parthian), both deriving from Proto-Iranian *arya- (meaning "Aryan," i.e., "of the Iranians"), argued to descend from Proto-Indo-European *ar-yo-, meaning "skillful assembler." In Iranian languages, the gentilic is attested as a self-identifier included in ancient inscriptions and the literature of Avesta,[a] and remains also in other Iranian ethnic names such as Alans (Ossetic: Ir - Ir) and Iron (Ossetic: Iron - Iron).
What Proto-Indo-European term means "skillful assembler?"
*ar-yo-
The Middle Iranian eran and aryan are oblique plural forms of gentilic er- (Middle Persian) and ary- (Parthian), both deriving from Proto-Iranian *arya- (meaning "Aryan," i.e., "of the Iranians"), argued to descend from Proto-Indo-European *ar-yo-, meaning "skillful assembler."
skillful assembler