The origin of the Armenian (Arm.) nominal suffix -agin is disputed. KLINGENSCHMITT (1982: 95) considers it as inherited and assumes that it is based on opaquepossessive compounds in *-gini- < *-gheh1-ni- ‘the going (Gehen)’, GREPPIN (1974: 14) suggests a derivation from an unspecified substrate, while SCHMITT (2001: 85) dismisses a link to the Middle Iranian (MIr.) suffix MPZ <-k(y)n'>, MPM, Pth. <-gyn> on formal grounds (cf. 3.2) without suggesting an alternative solution. This paper investigates the hypothesis that -agin is a borrowing from Iranian (Ir.) in spite of the formal difficulties. This idea has already been advocated by JAHUKYAN (1993: 262f.), who derives -agin via “-gēn (and -gīn?)” from *-k-aina-, identifying it with Arm. -kēn (likewise borrowed from Iranian), but does not venture to explain how -agin came to exist besides expected -kēn.