Originally, the definition was Niger, which is the German word for black was used in the early in the 1700's.
As slavery arose, the word, the word niger, became nigger and meaning black slave. It became deragatory, as in "Is that your nigger?" meaning property, rather than a person.
After, slavery was abolished, the word, nigger was still used by ignorant white people, who wanted to maintain the idea that whites were superior to blacks.
The word Negro or colored person was adopted instead, by the NAACP. Negro was considered acceptable, yet over time, it too became deragatory due to a lack of respect for the black community.
In the 1960's, Afro-Americans was adopted by the black community, but yet again they were still unable to get the full respect due to their own people's lack of ability to adapt to a civilized society.
For the most part lower class communities continue to perpetuate the idea that being a "nigger" means that you are also lazy, unmotivated, violent, and stupid.
Finally, today this term, "nigger" no longer applies strictly to black people who are now intelligent, educated, accomplished and law abiding citizens.
It now only reflects people regardless of skin color who continue to be lazy, unmotivated, violent, stupid or who maintain a welfare mentality.
When used between each other as in "What's up, nigger?" It is usually only used by those who remain ignorant and do not understand they are perpetuate a negative stereotype.
Seeing someone littering, "What a nigger!"
Seeing a lazy person, "She's such a nigger!"
Seeing someone trying to scam the welfare or other government agency, "That is so nigger!"