there was time when they were known as "muscovy". then in 18 century or smth, decide to rename. for some reason. probably, because at that time they controlled if not all, but a lot of ruthenia (rus) area, and that area had significant importance at that time. better look deeper into it on your own. have fragmentary knowledge about that area, and do not remember what was actual reason why they decide to name it as they have named.  also, might be similar as with persians. that their ruling guy one day decided that it will be named as iran, and that's all. curiously, initially a lot of countries did not recognized new name, including great britain. and when they sent letters, in address they placed "persia". eventually iranians got pissed about that. and said that if they will continue to do that, then their mail will not get delivered.
Latvia