Can I state my case?
"nigger" is a derivitive of "niggard," so you can really say that the two words have two separate histories, one had to exist before the other... But, besides tha fact that the oppressors flipped the script on the oppressed and made them believe that they were too greedy, always wanting freedom amungst other things...but that is just my view.
I believe that the origional definition slowly metamorphed into a slang word used by the elite class (wealthy, white landholding slave owners) that the set standard for the creation of the racial ephitet. It's sort of ironic really, if you think about it.
CB: If I'm the greedy pirate/capitalist/slavetrader/slave owner and I'm the "niggard," for the avenues I choose to accumulate wealth, and I have slaves that are my "property" or "chattel," which I provide and care for, then they must be my "niggers." Were they not one's always asking for more fertilizer to prepare the feilds for sowing, they were the ones asking for medical attention, food, a larger shelter to dwell in ect..?
So really, you can't just discard the fact that the two words are interrelated, becasue without niggard, there would have never a foundation nigger.