"Nigga did not only describe the lives loathed; it also described the lives loved."

• Yahdon Israel

From the context of Israel's article that is listed in the sources, "nigga" is a term that exists as a critique of the placement of black culture in broader society and discussion on the the self in that culture of oppression. There are obviously connotative differences between "nigger" and "nigga." The closeness of pronunciation is still enough difference between. You may have heard of someone saying the "n-word" and another person asking, "with the hard r?"

In terms of its understand in the academic community, it may be best to start with a quick discussion of African-American Vernacular English (AAVE). It is also known as Ebonics. According to John Rickford on linguistic society.org, AAVE grew out of African-American scholars desire to discuss Ebonics as a legitimate dialect of English instead as a derivative means of expression by an uneducated minority group. AAVE did enjoy broader discussion until the Oakland School Board wrote a resolution that states that AAVE was the primary language of their African-American students. One of the consistent aspect of Ebonics is in pronunciation. In the case of "nigga," the final consonant in omitted. So one could argue that "nigga" is essentially the same was "nigger." However, the use of connotative and contextual meaning of "nigger" and "nigga" are broadly different. People reacted differently when Michael Richards shouted "He's a nigger!" than when Gangsta Rap performs the song. The fact that African-Americans have taken to using a term that has historically been used to deride, dehumanize, or demean them can be seen as a type of agency. "Nigger" and "nigga" are the same word but who speaks truly changed the connotative meaning.

Historically, in mainstream culture in America, people usually see the term first used consistently among comedians like Richard Pryor and Paul Mooney. In an interview with Keith Olberman, Mooney states that while performing himself and writing for Pryor, one of their motivations for including "nigga" in the comedy was to "depower" the word. Later in the interview, he stated that he had stopped using the word. During this interview, he also states he started using the word in comedy for about 32 years. This interview was in 2006 during the Michael Richards fiasco at the Laugh Factory. So in mainstream culture, the usage of "nigga" likely begins in the early 1970s and was politically and critically motivated.

The word itself exists in our cultural contexts and means different things to every single person. Tupac Shakur turned the word into an acronym with positive connotations, "Never Ignorant Getting Goals Accomplished." The NAACP holds that the word in both its forms should not be used. It's meaning is truly diverse across racial boundaries.

The etymology of the two words come from Spanish "negro." It was broadly accepted to refer to African-Americans as Negros until the mid-20th century. One of Fredrick Douglas most famous writings "The Meaning of July Fourth to the Negro" confirms the usage of the term among free blacks during the late antebellum period. W.E.B Dubois used both "negro" and "black" in his writing. So even going into the 20 early mid-20th century, the writings of educated African Americans do not use the word "nigga," however that is to be expected. DuBois did have some writing about the meaning of "nigger" and other terms used to generalize the black community. He in fact preferred the word "negro"as it is inaccurate. He states that African-Americans are indeed brown. So that is another aspect to consider. There may not have been slaves calling each other "niggas" but they were likely using some term to broadly categorize people. However, only relying on the primary sources written by educated black men betrays several other groups within the black community like women and the uneducated, these voices and perspectives are likely lost to us so we can only speculatively. Black people were definitely been using the term before Richard Pryor became popular in the mainstream.

As I stated previously, through Ebonics "nigga" is "nigger" interpreted through another culture. The two words are inexorably connected to one another in which the existence of one almost guarantees the existence of the other. I will conclude with a quote from Dubois.

"Your real work, my dear young man, does not lie with names. It is not a matter of changing them, losing them, or forgetting them. Names are nothing but little guideposts along the Way. The Way would be there and just as hard and just as long if there were no guideposts, but not quite as easily followed! Your real work as a Negro lies in two directions: First, to let the world know what there is fine and genuine about the Negro race. And secondly, to see that there is nothing about that race which is worth contempt; your contempt, my contempt; or the contempt of the wide, wide world."

-W.E.B Dubois

Sources

http://thenewinquiry.com/essays/coming-to-america/

http://www.linguisticsociety.org/content/what-ebonics-african-american-english

http://www.virginia.edu/woodson/courses/aas102%20(spring%2001)/articles/names/dubois.htm

There's a fantastic book written by Jabari Asim called The N Word that dives deep into the history of the word.

Asim shows that you can find ironic uses of the word "nigger" dating at least back to 19th century literature written by black Americans. "Nigga" also doesn't have a hard and fast first appearance, but Asim argues that the popularization of gangsta rap is the most important factor in that word's popularity:

Rappers and others... have chosen to indicate their efforts to turn insult into affection by giving [nigger] a new spelling.

According to such thinkers, "nigga" can be used without malice between blacks and also to distinguish acceptable forms of black behavior from uncouth ones.

This being said, Asim goes on to express a doubt in the validity of this "new" word, and feels it does not reconcile correctly with acceptable behavior or a complementary tone.

The only non-deleted answer I've seen doesn't seem to have a when, and doesn't doesn't really seem to have a why, so I'll attempt to answer those questions for you as simply as possible.

I'm a linguist who does research on African American English; I coauthored work on contemporary uses of nigga, and you can read the (somewhat technical) extended abstract here..

The short answer for why is that -- in some registers of AAE -- it has become semantically bleached and is a generic term like guy, distinct from the slur nigger (which, in these varieties, seems to be a separate word). By default it refers to human males, but it is not inherently specified for 'race' nor is it necessarily always male or always human. Moreover, there are a number of grammatical constructions that make use of nigga where it's easier to think of the word as part of a term, either a pronoun (a nigga meaning I/me), a term of address (nigga for greater social distance, my nigga for closer social distance), or an honorific (my nigga _______ for friends, that nigga _____ for people who are not personal friends, and this nigga _____ for people the speaker is mocking/going to mock).

As for when, the earliest we could find (somewhat) mainstream use of nigga was the late 1960s early 1970s. You can start to see the change in use in The Last Poets' "Niggers are Scared of Revolution", or in Melvin Van Peebles' classic 1971 blaxpoitation film Sweet Sweetback's Badasssss Song, etc.

It was likely in some kind of use as far back as we can find reliable representations of black speech in varying degrees of semantic bleaching, but it's not until around the rise of the Black Power movement that you really start to see people reclaiming and reshaping the word.

A few other important things to note:

(1) The AA community did not begin to do this. There is not one monolithic black community. A significant number of black Americans do not speak AAE natively, and those who do may or may not speak a variety that has this use. They may not condone it. It's a complicated social issue, and it's important that we not take a reductionist view of ~40,000,000 people in the US.

(2) it's generally best for someone who does not speak this variety of AAE natively to just avoid using it. There are plenty of ways to not say nigga, and if you're not someone who natively knows how to use it and has the pragmatic ability to determine when it's appropriate, just don't.

(3) the above point is doubly true for white people -- claiming a linguist said it's a different word is not gonna get you out of a shitty situation when you say something everyone hears as a slur.

Future linguist here! I just wrote a paper that was very related to this topic. Thenerd's comment mentions an important aspect, but doesn't go into too much detail. In African American vernacular English (commonly referred to as ebonics, which is a little different), many speakers drop a postvocalic /r/ (when /r/ is not followed by a vowel) in most contexts. This means that for speakers of that dialect, "nigger" is pronounced as "nigga" (can't cite on mobile, but William lebov researched AAVE phonetics & phonology).

African Americans have used the word throughout the 19th century when referring to each other as a form of not only solidarity, but a recognition of the history of their people in this country (will add a source for this when I get home, I promise. For now, take it with a grain of salt) and it really gained widespread usage in the 80's and 90's with the rise in popularity of hip hop in the US (again, will add citation later tonight).

Very recent research by /u/languagejones has discovered that "nigga" is now undergoing semantic bleaching (loss of meaning) and where it once had the semantic sense of [+human +African American +male] it now is being used by many speakers for referents that are not African American, or even human in some cases. For example, now statements like "the Irish nigga with the weird smile" can be used by speakers of AAVE. However, this research is not intended to justify use of the word by any person, just to document AAVE speakers. It's still very touchy and someone can still easily offend a Black person by saying it. I highly recommend taking a look at this research, although it was only presented at a linguistic journal's yearly summit (2015) and has not yet been peer-reviewed. The submission does provide ample proof against every country-argument for their findings.

To the mods: I just got out of work. I will add my sources when I get home and can pull up my paper.

Delete this if it isn't relevant but I was watching an episode of Good Times, early 70's, a few weeks ago and they used it in passing. James was in a bar and a drunk was trying to talk to him. He said "N, do I know you?" I wasn't sure I heard it correctly and replayed it to make sure. It seemed weird because I'm pretty sure that was a family show on in prime time. Can someone elaborate on if that would have made it on air.

Edit: I know this is a sensitive subject but why the down votes. I feel like I asked a legitimate question