In the Ili valley of Xinjiang province, in China, there is an ethnic group called the Sibe, who speak a dialect of Manchu, and use a form of the Classical Manchu language as their written language.
One of the odd differences between Sibe and Manchu is that their words for East and West are reversed. The Manchu words for East and West are (respectively) dergi and wargi, while the Sibe words are vɛrɣi and dirɣi. (They're reversed...trust me).
As far as I know, no one has ever explained this. It is generally assumed that the Manchu words originally referred to the rising and setting of the sun. So, for example, dergi, "East", is related to words like dekde-, "rise", deye-, "fly", desi, "upward"; while wargi, "West", is related to words like wasi, "downward", wasihūn, "low", etc.
But then why are they reversed in Sibe? The sun surely rises and sets the same for the Sibe as for the Manchus.
The Manchu language is based on the language of Nurhaci and his people, who lived on the Suksuhu river. It is probably a sister to the Sibe language, both being dialects of Jurchen. The Sibe do not consider themselves Manchus, and they did not come from the Suksuhu river area, they lived along the Amur river.
Guess what? The Suksuhu river runs West, and the Amur river runs East. If dergi and wargi originally meant "upstream" and "downstream", then that would explain why they are now reversed in Sibe and Manchu.