Negro was used by masters to separate the "Negros" from the "humans"(whites). Read the diaries of the time. The "Negro" was essentially a beast. You never see whites back then refer to themselves as Caucasians or European Americans. They were always "white".
Even today, we don't call ourselves Caucasians in normal speech. When white people use the term "negro", it's basically a way to introduce themselves as "rednecks".
I really, really, really dislike ever having to check myself off as 'causasian'. I don't feel any particular affinity to the people living in the Caucasus mountains. I especially don't speak Chechen. I don't even think English is a close relative.
Negro was used by masters to separate the "Negros" from the "humans"(whites). Read the diaries of the time. The "Negro" was essentially a beast.
I am now browsing through an original 1856 printing of the 383 page pro-slavery apologia An Essay on Liberty and Slavery written by Albert Taylor Bledsoe .
The following terms are interchangeably used in Bledsoe's book:
"the African"......."justify the servitude in which the providence of God has placed the African."
"the African race"......."the case with the African race in its present condition....."
"the blacks"......."elevation of the blacks by Southern slavery..."
"the black men"......."We shall refuse to head a conspiracy against the good order , the security, the morals and the very lives of both the white and the black men of the South."
"negro"......."An independent negro state was thus established in Hayti."
The pro-slavery arguments of the time (and Bledsoe wrote 383 pages of them) did not claim that (blacks, Africans, negroes) were "not human". The pro-slavery arguments of the time claimed that that they were humans created by God with a lack of industry and morals and therefore needed the control of the master just as a child needed the control of the parent.
In short, the terms "balcks", "Africans" and "negro" were used interchangeably with no difference in meaning between them, there was no connotation of "human" vs "non-human", only "African" was capitalized, and "negro" was used to describe both a slave and an independent negro republic.