Nigger is a slur used against black people. It is often used by racists.
The word originated as a mispronunciation of the feminine form of the word "negro", which is "negra". In Portuguese, "preto" means the color black and "negro" means black people, but in Spanish, "negro" means both the color black and black people.
Before 1865, many black people in the United States were slaves. In this time, "nigger" often meant a slave. Writers like Joseph Conrad, Mark Twain, and Charles Dickens used this word in their books, even in non-racist ways.
In the 21st century, many black people have "taken back" the word niggеr by using It's derivative "nigga". They use it as a slang word. Some groups are trying to make the use of the word "nigga" normal for everyone.
Also used in South Park episode “With Apologies to Jesse Jackson” Season 11 Episode 1