In 1985, Soviet linguist Igor M. Diakonoff noted the presence in Classical Armenian of what he calls a "Caucasian substratum" identified by earlier scholars, consisting of loans from the Kartvelian and Northeast Caucasian languages. Noting that Hurro-Urartian-speaking peoples inhabited the Armenian homeland in the second millennium BC, Diakonoff identifies in Armenian a Hurro-Urartian substratum of social, cultural, and animal and plant terms such as ' "slave girl" ( ← Hurr. "al(l)a(e)ḫḫenne"), "cov" "sea" ( ← Urart. "ṣûǝ" "(inland) sea"), "ułt" "camel" ( ← Hurr. "uḷtu"), and ' "apple (tree)" ( ← Hurr. "ḫinzuri"). Some of the terms he gives admittedly have an Akkadian or Sumerian provenance, but he suggests they were borrowed through Hurrian or Urartian. Given that these borrowings do not undergo sound changes characteristic of the development of Armenian from Proto-Indo-European, he dates their borrowing to a time before the written record but after the Proto-Armenian language stage.