Belarus comes from Belorussia, which is literally just "White Russia" in Russian. Historically several different regions in the area were defined as "Russia" or "Rus" with a modifier in front: Black Russia (modern Western Belarus), Red Rus (Southeastern Poland/Northern Ukraine), Great Russia (the historic lands of Russia centred around Moscow), and Little Russia (mainly Ukraine). Now why White Russia was called White, there is no definitive answer. Various theories exist, which you've noted, but the only thing we can say for certain is these terms date back centuries (White Russia, or a version of it, is first recorded in 1381).

1. Slavs used colours as attribute of cardinal directions. So you had for example tribes like White Croats or White Serbs, areas like Red Rus, White Rus, Black Rus. So White Rus = Northern Rus.

2. Rus =/= Russia. Rus was country of East Slaves, that was created in IX century by Vikings that traveled by rivers to the Black Sea and the Byzantine Empire, in X century it was christianized, next there was fragmentation of country to the many small principalities, and ceased to exist after mongolian invasion in XIII century. Most of Rus principalities were occupied by Mongols and had to pay tribute to them to the XIV century, until they were strong enough to reject the dependence to them. There was several centers of unification of country, one of them was Great Principality of Muscowy, that latter created Russia from areas that was conquered by them. The other was Grand Duchy of Lithuania, that conquered areas of modern Ukraine and Belarus, later merged with Kingdom of Poland in Commonwealth of Both Nations. So Rus is ancestor country to Belarus, Ukraine and Russia, this 3 countries have many common with each other, but because they weren't part of one country by several houndreds years the differences between them are so big, that they have separate cultures, languages, ethnicity.

3. English language doesn't takes it into account. Maybe because in XVIII and XIX century Russia tried to justify the conquest of the areas of Belarus and Ukraine as reconstruction of Rus, and their propagand tried to claim that the Ukrainian and Belarussian are local dialects of Russian, and people from this area are Russians.

Hi, it seems that there's no definitive answer. You may be interested in these responses in previous threads:

• Would the average citizen in the USSR call themself a Soviet or a Russian? by /u/kieslowskifan

• Is there any connection between the term "White Russian" for anti communists and the translation of Belarus "White Russia?" by a now-deleted account

• "Ukraine" versus "the Ukraine": A mere difference of terminology, or a politically charged statement? by /u/watermark0n

These posts are all archived now, so if you have follow-up questions for any of the users, ask here and tag their username to notify them.

• Nobody knows why it is exactly "white", even here in Belarus there are plenty of mostly romantic versions.

• The most accepted theory now is the concept of a Belarusian historian Ales Bely, saying that "Ruthenia Alba" (White Rus) is a cabinet term used by Western medieval scholars and maybe originated in Arabian sources

• The fact is that the name "Ruthenia Alba" was used mainly for a Novgorodian lands for centuries, and was moved to modern Belarusian lands just about 500 years ago. So it is a migrating name and therefore this "White" part cannot have any real meaning.

• Belarusian nationalists in 19th century selected the name Belarus for their nationalism just because it was slightly more popular than other variants like Kryvia. Their initial idea was to use a name "Litwa" (Lithuania), but it was already taken by Lithuanian nationalists.