Rus is what these people called themselves. They were folks lured to that part of the Mediterranean by promise of work in the Byzantine military as Varangian Guards.
A subset of these Norsemen sailed up the Dniper to what is today Kiev and setup Kievan Rus. They ruled over and assimilated the the Slavic, Bulgar, and Turkic peoples of the area. In the Middle Ages, the Mongols came and destroyed Kiev, murdering just about everyone inside, leading to fragmentation into multiple polities like Moscow, the Novgorod Republic, and Vladimir.
The Rus ethnonym lives on in the name of the Russians, Rusyns, Ruthenians, Belarussians, and others!
Varangians came primarily from todays Sweden, and were initially going inland into the today's Estonia, Belarus and Russia from north, from the Gulf of Finland, using rivers. The group of them called Rus under the leadership of Rurik created Novgorod in 862. About 20 years later they've also conquered Kiev (some 900km more to the south). They were initially raiders, but over time they've conquered the local Slavs, established their rule and became very important traders, as they've created the trading (and also slave) routes all across the continent from the Baltic in the North down to the Black Sea - using huge rivers like Volga and Dneper - trading in south with Byzantin empire and Abbaside Caliphate. It was one of the main trading routes between West/North Europe and Arab world of that age.
And as their presence grown stronger, the Rus started more frequently raiding the Byzantin Empire, sacking even the big Constantinople a few times. To stop these attacks, in 10th century the Byzantines did the same move as king Charles the Simple did in Francia with Normans, they gave Varangian leaders some titles and employed them all as a royal guard. Problem solved.
And then, as you've said, the viking era was over, and they assimilated into the Slavic population (just like Bulgars and others did).
Another interesting note, the Rus ethnonym also got into many Slavic languages as a word for fair blonde or reddish-blonde hair ("русая" in Russian, "rusa" in Serbian/Croatian, etc.). In Serbian 'rus' was historically used in folk language with a meaning 'red', for instance for skin rush, names of some herbs, etc.
The ancient Greek word for "Slave" is δοῦλος, pronounced "doulos". I'm struggling to see how that comes from "Slav". The sources I've looked up say the derivation is uncertain, but noone mentions "Slav" as a possible origin[1]
Yes, but I believe it was Latin, not Greek (Constantinople was a capitol of Easter Roman Empire, and they used both Latin and Greek). Latin term Sclavi that meant Slavs started to be used for slave servants, because there was so many of them.
> these poor people served as a "buffer" against the Mongols, saving Europe from the slaughter ...
You mean saving Western Europe :)
Mongols ran over (and did a lot of slaughter in) the most of Eastern and Central Europe, including Poland, Czechia, parts of todays Germany, Hungary, Bulgaria, Croatia and Austria. There was no "buffer" that stopped them, they've stopped eventually because their Great Khan died. As the leadership broke down and fights for power arose, they've been forced to return back home.
Mongols invaded Eastern and Central Europe several times, but they always turned back. There are at least two common explanation for that.
First, European countryside was infested with castles. Defeating the king and sacking his capital wasn't enough to pacify the land. Mongols would have had to deal with every local warlord separately, and Europe wasn't worth the trouble.
Second, Mongols were getting too far away from the steppe. Their armies could not stay in Europe in the long term due to the lack of large enough pastures.
The hills and forests of Western Europe were also unfavourable for their preferred cavalry based tactics. And even the damp weather was against them since they couldn’t use their compound bows in the rain.
Well, they were basically a highly-mobile light cavalry/archers combination, so while they progressed very fast they were not spending much time sieging heavily fortified cities or going into mountains and other hard to cross terrains. Also it took Europeans a while to learn how to fight them efficiently, but eventually they did figure out that European heavy cavalry is a good match for them. So it's not they were "unstoppable", they simply avoided hard targets, and pillaged the villages and other less defended areas, and moved quickly through disorganized European kingdoms fighting each other.
That's not unique to the Mongols. Another easy example would be Alexander of Macedon. History is filled with great empires, many of them expanding, which fell or contracted after the leader passes.
PS. I wonder what - if anything - implications that has for leadership or management - you know, the whole achievement falling apart, missing one individual ...
(Or, to project management - low "bus factor", so to speak ...)
The land was already settled by slavic and finnic tribes, whose experience of this is lost to us. The norse made their own settlements and assumed rule over the existing groups. Eventually the norse and finnic groups had more or less fully assimilated with each other and into the local slavic population forming the rus'.
If you go even further back, it was people from the Caucasus/modern day Ukraine that wiped out the male population of Europe and settled Europe. The same group of people that also branched off and settled in Iran and India. The speakers of PIE. Fast forward about 2000 years and the Scandinavians went back and assimilated with local tribes to form the Rus.
Various linguists have done reconstructions of what PIE might have sounded like from projecting back through the descendent languages. There are several examples on YouTube.
Obviously none of them are 100% accurate but they may capture some of the feel of the language.
Modern Sweden was only a part of origins of vikings. If it is known that those people are specifically Swedish vikings, then it makes sense to highlight that.
