The word for "we" in some languages. (Being Norwegian, I am giving more details of Norwegian dialects than of other languages' dialects.) Now let's see if I can explain this in a way that won't make linguists chew their arms off...:
Pronouns are very basic elements of language, and are very often irregular. Now, in terms of meaning, English "we" and "us" are really the same word - only different grammatical forms... 1/*
But "us" is not formed by conjugating "we" in a regular way - it is an entirely different word.
And this goes all the way back to the Proto-Indo-European language, thousands of years ago: The subject form was *wey and the object form *nsme (sort of, possibly, probably).
English, German, Norwegian etc. have inherited both forms, with more or less the same function.
But in the red languages, the object form took over the function of the subject form. Like latin "nos" and its descendants.