This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

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) and Iron (Ossetic: Iron).
What century did terms referencing Iran begin to be recorded?