Some people like Tupac claim that it stands for "Never Ignorant, Getting Goals Accomplished" or "Never Ignorant about Getting Goals Accomplished." We all know that this is a bunch of macaca. This word was actually developed by people who couldn't be bothered spelling out the whole six letters of "nigger," and shortened it to the easier, five-letter version of "nigga."
Demetrius: Yo son, let's never be ignorant about getting goals accomplished!
Asante: Nigga, get out my face wit dat Dr. Phil shit!