In c. 679, Khan Asparukh conquered Scythia Minor, opening access to Moesia, and established the First Bulgarian Empire, where the Bulgars became a political and military elite. They merged subsequently with established Byzantine populations, as well as with previously settled here Slavic tribes, and were eventually Slavicized, thus forming the ancestors of modern Bulgarians.
The remaining Pontic Bulgars migrated in the 7th century to the Volga River, where they founded the Volga Bulgaria; they preserved their identity well into the 13th century. The Volga Tatars and Chuvash people claim to be originated from the Volga Bulgars.
The etymology of the ethnonym Bulgar is not completely understood and difficult to trace back earlier than the 4th century AD. Since the work of Wilhelm Tomaschek (1873), it is generally said to be derived from the Common Turkic bulğha, bulga- or bulya ("to mix"; "to become mixed"), which with the consonant suffix -r implies a noun meaning "mixed". Other scholars have added that bulğha might also imply "stir", "disturb", "confuse". and Talat Tekin interpreted bulgar as the verb form "mixing" (i.e. rather than the noun "mixed"). Both Gyula Németh and Peter Benjamin Golden initially advocated the "mixed race" theory, but later, like Paul Pelliot, considered that "to incite", "rebel", or "to produce a state of disorder", i.e. the "disturbers", was a more likely etymology for migrating nomads. According to Osman Karatay, if the "mixed" etymology relied on the westward migration of the Oğur (Oghurs), meeting and merging with the Huns, north of the Black Sea, it was a faulty theory, since the Oghurs were documented in Europe as early as 463, while the Bulgars were not mentioned until 482 – an overly short time period for any such ethnogenesis to occur. However, the "mixing" in question may have occurred before the Bulgars migrated from further east, and scholars such as Sanping Chen have noted analogous groups in Inner Asia, with phonologically similar names, who were frequently described in similar terms: during the 4th Century, the Buluoji (Middle Chinese b'uo-lak-kiei), a component of the "Five Barbarian" groups in Ancient China, were portrayed as both a "mixed race" and "troublemakers". Peter A. Boodberg noted that the Buluoji in the Chinese sources were recorded as remnants of the Xiongnu confederation, and had strong Caucasian elements.
Another theory linking the Bulgars to a Turkic people of Inner Asia has been put forward by Boris Simeonov, who identified them with the Pugu (僕骨; buk/buok kwət; Buqut), a Tiele and/or Toquz Oguz tribe. The Pugu were mentioned in Chinese sources from 103 BC up to the 8th century AD, and later were situated among the eastern Tiele tribes, as one of the highest-ranking tribes after the Uyghurs. According to the Chronicle by Michael the Syrian, which comprises several historical events of different age into one story, three mythical Scythian brothers set out on a journey from the mountain Imaon (Tian Shan) in Asia and reached the river Tanais (Don), the country of the Alans called Barsalia, which would be later inhabited by the Bulgars and the Pugurs (Puguraje).