  Let's put this in easy English:  Lars Johanson  Azerbaijanian koiné refers to a Turkish language in the geographic region of Azerbaijan. The term Azerbaijanian when used by linguist does not necessarly refer to the Oguz Turkish language of the republic of Azerbaijan, but rather the Turkic languages in the geographical Azerbaijan. Non-Oguz Turkish languages like Kalaj are also often considered as Azerbaijanian so this term should not be equated with Azerbaijani or Azeri some scholars like Johanson do, but it is not shared by everyone, and Johanson Azeri is more broad than generally aknowledged.  Your second source is not Glanville Price but the Turkish scholar Tourkhan Gandjei, I suppose you will claim him as originally Azeri, but I won't debate about his origine. Note the contradiction: The earliest Azeri texts date from the 14th c.; their language is that of contemporary Anatolian Turkish (Old Ottoman) texts. In short, the said Azeri of the 14th century was nothing more than Old Ottoman language. Then he continues: Azeri underwent the influence of Central Asian Turkic literary works, grammatically, lexically, adn to some extend orthographically. Up until then, same as several Turkish population like those in present day Eastern Turkey or Irak. I suppose you will call them as Azerbaijani, that's open to debate. Here, your comparaison with Germanic and English does not make sense, as Azeri, Turkmen and Turks can still understand eachother quite well.  Your other source is Lev Gumilyov, but Soviet historians ethnogenic studies are not well perceived, particularly those of scholars like Lev Gumilyov.  There are several sources which consider the language spoken there as Turkish for the given period, your reference refering to a lingua franca for example can also be replaced by this one: The lingua franca of the entire Caucasus was Turkish, then termed Tatar. (The North Caucasus barrier: the Russian advance towards the Muslim world by Marie Broxup, Hurst, 1996, p. 71)   That they were Azeri or not is open to debate and interpretation, stick in doing a synthesis of what the sources say, and they are all contradictory... so I guess no one disagree to the fact that it was a Turkic language.  Moewy opposition to the use of Azerbaijani as different than Azeri has ground, Azerbaijani read as people from Azerbaijan, it's akward to use it to refer to any particular language.  Also is akward to have an Azeri language prior to the existance of an Azeri ethnic identification setting them apart for several centuries.  Azerbaijani national identity is a recent growth Source:New Terror, New Wars by Paul Gilbert, Edinburgh University Press, 2003, p. 61  Azerbaijan features an official national identity based on an improbable blend Source: National Identity and Globalization by Douglas W. Blum, Cambridge University Press, (2007) p. 106, note that ut's from  Cambridge University Press.  the Azerbaijani national identity is very recent. Modern Hatreds by Stuart J. Kaufman, Cornell University Press, 2001, p.56  Azerbaijani national identity is a relatively recent formation Source: Language Policy in the Soviet Union by Lenore A. Grenoble, Springer, 2003, p. 124  There are two opposing view, Gereth M. Winrow present them as such: In recent Western literature at least two conflicting arguments have emerged with regard to Azerbaijani identity. According to Audrey Alstadt, Azerbaijani nationalism was fostered among the intelligentsia in the Russian-occupied part of Azerbaijan by the end of the nineteenth century. These Azerbaijanis regarded themselves as 'Azerbaijani Turks', in spite of the fact that until the Russian conquest earlier in the century, all Azerbaijan had been a part of the Persian Empire. Without the pressures of the industrialization and Russian occupation, the 'Azerbaijanis' remaining within the Persian Empire continued to identify themselves with Persia. Shireen Hunter has argued, though, that Azerbaijani nationalism in the territory of today's independent Azerbaijan only really took shape as a result of Stalin's deterination to stamp out the Iranian heritage in the area. In Soviet Azerbaijan a Turkish consciousness was artificially instilled in most of the inhabitants...''   Some call the given language for the given period, Turkish, Turkic, Azeri... no one oppose either way it was Turkic.