Old southern pronunciation or slang for negro. Generally considered disparaging today particularly when used by non-blacks. When the word is used by "nig-nogs", as the Queen Mother of England might have called them, it is something like an acknowledging term saying " yes, we niggers, we accept who we is, we have a shared history, we are "brothers", "niggers"
It used to be that niggers were property. Now that niggers are free and can do whatever they want to do, now that society has been niggerized, white kids want to be niggers too.