Procopius of Caesarea / c. AD 500 – c. AD 565/ was one of the most prominent Byzantine scholar from Palestine. Accompanying the general Belisarius in the wars of the Emperor Justinian I, he became the principal historian of the 6th century, writing the Wars of Justinian, the Buildings of Justinian and the celebrated Secret History. He is commonly held to be the last major historian of the ancient world.
"Beyond the Sagins lived many Hunnic tribes. Expanding from that point country is called Evlisia (Procopius evidently used information from "Anonymous Periple of Pontus Euxinus," where this country beginning form the Sagins dwelling places and up to Don and the Azov Sea is actually spelled "Evdousiya"), Its coastal area, aswell the interior is inhabited by barbarians up until the so-called "Meotian swamp " (Sea of Azov ) and the river Tanais (Don), which flows into that "swamp". In turn, the swamp overflows into Pontus Euxinus (Black Sea). The people who live there in ancient times were called Cimmerians, now they are called JUtigurs. (Book .ІV.4, The war with the Goths). "
"A huge number of Huns in ancient times, who back then were called Cimmerians, lived in these areas, that we have mentioned, and one king ruled over them. Then ruled over them a king who had two sons, one of these was called Utigur and the other - Kutrigur. When their father died, they shared the rule and named their subjects in their own names. And by my time, part of them are still called Utigurs and the other part - Kutrigurs ... (Book .ІV.5, The war with the Goths). ”.