Proto-Slavic—the idiom from which the modern Slavic languages developed—emerged in the first half of the 2nd millennium BC. The Early Slavs lived in the plains north of the Carpathian Mountains or along the middle course of the Dnieper River. Their expansion accelerated after the fall of the Hunnic Empire in the middle of the 5th century AD. Significant Slavic-speaking groups moved across the Lower Danube and settled in the Balkan Peninsula. By the end of the 7th century, Slavic became the dominant language in most places in the Balkans. Studies of the South Slavic languages revealed that Bulgarian and Serbian developed for centuries in two distant territories, separated by significant non-Slavic groups.