Bulgaria was named after the bulgars, an oghur Turkic people. But certainly thats not what they were referring to, as thats very recent history.

But just the title is wrong, as asian just designates people from a continent today.

Siberia is known to be the origin point of the most clusters of east asians proper (northern). China, Japan, Korea, all of those are rather southern populations, or really a mix of southern and northern elements, much closer to southeast asians than to northern asians. True northern east eurasians are groups like the Ket, Evenki, Nenet, Eskimo-Aleuts. Tungusic, Ket people are from the same language family as the Na Dene native americans such as the Athabaskans like Navajo, the Dene-Yeniseian family.