Esegels were a dynastic tribe, of Turkic linguistic affiliation, in the Middle Ages who either joined the Itil Bulgaria state and were assimilated to Bulgars. Numerous records about Esegels in the sources in many languages, in connection with many historical subjects, and across the span of the Eurasian steppes left numerous variations of their name. M. Räsänen suggested Uralo-Altai etymology of this word: Es-kil, Es-gil "Old city", which may conflict with the older Chinese phonetization of Āxījiē 阿悉結. Gumilyov initially linked the Izgils to the Sijie of the Toquz Oghuz; only to later re-identify Izgils with Xijie, another Tiele tribe. Róna-Tas proposes an Iranian origin: Western Old TurkicAskil, Äsägäl < äθägäl < haθyaka arya "the very aliens". Zuev proposes other connections with the Chigils living near lake Issyk-Kul, the Āxījiē of the Nushibitribal confederation of the Western Turkic Khaganate, and the Xionitepersonal nameAskil/Askel, as mentioned in the Chronography of Theophanes the Confessor :
"the same month ambassadors of Askil/Askel, the king of Hermihions, a tribe living among barbarians near the ocean, came to Constantinople".
Zuev noted that other scholars than himself and Cen Zhongmian, e.g. Harmatta, Klyashtorny linked the Izgils to the Sijie 思结 of the Toquz Oghuz confederation. However, Zuev distinguished the Izgil from Igil 思结 ; though Zuev controversially links the Sijie < Igil to the Bulgarian clan Uokil and the Indo-European-speakingAugaloi in Transoxania. A Chinese annalistic account in 651 CE of the Western Turkic Khaganate listed five west tribes collectively as Nushibi and noted that Kül-Irkin, the leader of first tribe, Āxījiē, "was most prosperous and strong, the number of his soldiers reached several tens of thousands". Arab ambassador Ibn Fadlan, who visited Itil banks in the 921–922, mentioned in his journal the Bulgarian tribe Askel, besides the Bulgars proper, the Suvars, the Bersula, and the Barandzhar. Persian ethnographer Ahmad ibn Rustah listed three branches of the Volga Bulghars: "the first branch was called Bersula, the second Esegel, and the third Bulgar". Among other writers who mentioned Esegels, the Persian “Geography“ of 982 named Ishkils as one of three Bulgarian tribes, who were constantly conflicting among themselves. Gardizi, the author of the composition Zain al-ahbar, wrote: "Between possessions of Bulgars and possessions of Eskels, who also belong to Bulgars, is a Magyar area. These Magyars are also a Türkic tribe". Constantine Porphyrogenitus wrote that endoethnonym of the "Magyar Türks" was Savartoiaskaloi, i.e. Savart and Eskel. Yu.A.Zuev summarized that "It is held that Eskels merged with Hungarians. Zuev proposes that the ethnographic groupSzékely'' are Esegels' descendants". However, Róna-Tas rejected identification of Esegels with Székely, as well as the link between the names Esegels and Chigils, on historical and phonological grounds
