was early contact between Armenian and Anatolian languages, based on what he considered common archaisms, such as the lack of a feminine gender and the absence of inherited long vowels. However, unlike shared innovations (or synapomorphies), the common retention of archaisms (or symplesiomorphy) is not considered conclusive evidence of a period of common isolated development. There are words used in Armenian that are generally believed to have been borrowed from Anatolian languages, particularly from Luwian, although some researchers have identified possible Hittite loanwords as well. One notable loanword from Anatolian is Armenian xalam, "skull", cognate to Hittite ḫalanta, "head". In 1985, the 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 ałaxin "slave girl" ( ← Hurr. al(l)a(e)ḫḫenne), cov "sea" ( ← Urart. ṣûǝ "(inland) sea"), ułt "camel" ( ← Hurr. uḷtu), and xnjor "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. Contemporary linguists, such as Hrach Martirosyan, have rejected many of the Hurro-Urartian and Northeast Caucasian origins for these words and instead suggest native Armenian etymologies, leaving the possibility that these words may have been loaned into Hurro-Urartian and Caucasian languages from Armenian, and not vice versa. A notable example is arciv, meaning "eagle," believed to have been the origin of Urartian Arṣibi and Northeast Caucasian arzu. This word is derived from Proto-Indo-European *h₂r̥ǵipyós, with cognates in Sanskrit (ऋजिप्य, ṛjipyá), Avestan (erezef), and Greek (αἰγίπιος, aigípios). Hrach Martirosyan and Armen Petrosyan propose additional borrowed words of Armenian origin loaned into Urartian and vice versa, including grammatical words and parts of speech, such as Urartian eue ("and"), attested in the earliest Urartian texts and likely a loan from Armenian (compare to Armenian , ultimately from Proto-Indo-European *h₁epi). Other loans from Armenian into Urartian includes personal names, toponyms, and names of deities. Loan