Good question. I have another question in this topic. This question actually has been bothering me for decades. Back in Soviet Union we actually had to learn Primary chronicle and there was such sentense:

The four tribes who had been forced to pay tribute to the Varangians—Chuds, Slavs, Merians, and Krivichs—drove the Varangians back beyond the sea, refused to pay them further tribute, and set out to govern themselves. But there was no law among them, and tribe rose against tribe. Discord thus ensued among them, and they began to war one against the other. They said to themselves, "Let us seek a prince who may rule over us, and judge us according to custom"

Now to the question. Back in 70s and 80s (also now) Russians called us (Estonians) Chuds, but in this chronicle it seems that Chuds were actually someone else. What is known about those mysterious Chuds? Did they become what we know as Russians now-days?

No there's no definitive point but primary sources do seem to indicate that the word emerged as applying exclusively to Norsemen in what is now Russia, Ukraine, Belarus and bits of Lithuania but then came to encompass both Norsemen and Slavs.

One factor that may have helped bring them together was their joint expansion into the North-East of Russia. But the process is still poorly understood. Here is an [earlier comment] (https://www.reddit.com/r/AskHistorians/comments/455zlz/how_were_the_kievan_rus_related_to_the_vikings/czw9ri8/) where I tried to cover some basics. And here's [another thread] (https://www.reddit.com/r/AskHistorians/comments/5ea8bo/why_moscow_and_not_novgorod/dacr555/) where I go into details. To sum it up, this coalescence of the Norse and Slavs into a single group might be exactly due to their joint - or at least concurrent - expansion into a new and possibly hostile Finno-Ugric environment. (I don't think the archeological evidence we have is conclusive, though, as to their relations vis a vis these newcomers). The patterns of settlement are quite telling, though. As the Norse and the Slavs moved east, every time the picture is the same - first there's an isolated settlement by the water, usually in a defensible position, that shows signs of joint Norse and Slavic occupation and later it is abandoned or declines in importance but there's now a bigger and more important joint settlement where they cohabitate with the Finno-Ugric inhabitants of the area. So this was roughly the same process that we can see earlier in the Ilmen Slav lands, case in point being the Ryurikovo Gorodische/Novgorod pair, for example.