farther back is a lot of conjecture about linguistics from largely unreliable sources. that isnt to say all these theories are false, but they almost never have real archaeological backing or reliable sources. for example there is a document about someone claiming the term khagan is used by rus people for their leader, and the person replying is saying that he has never heard that and thinks its incorrect. furthermore it could be that rus referred to their leader as hakan, and the original person may have misheard this and assumed khagan. as we have real evidence the scandinavian influence was in rus before rurik, but almost none about khaganate influence.  the same goes for all these theories, someone says x sounds like y and therefore x comes from y group, yet if theres no archaeological evidence this is junk, and its entirely possible that both x and y descend from group z a thousand years before that and they just maintained the same word, or that x heard the word through trade and copied it because its useful/interesting.
Russian Federation