score:3
According to the June 2016 Oxford English Dictionary Online, it is a colloquial term for "Negro":
U.S. colloq. and regional (chiefly south.). Usu. offensive. Origin: A variant or alteration of another lexical item. Etymon: Negro n. Etymology: Representing a colloquial pronunciation of Negro n.
The OED also has it being squarely a 20th century term, arising in the early century and not being seen much after the 1960s. I grew up in the South in the 1980s and never heard it, although I did hear other derogatory language.
It was definitely not any less derogatory than other racist terms.