nigra (n., adj.)
by 1944, American English, reflecting a white Southern U.S. pronunciation of Negro, but it was held to be a compromise made by those whites who had learned to not say nigger but could not bring themselves to say Negro, and it was thus deemed (in the words of a 1960 slang dictionary) "even more derog[atory] than 'nigger.' "

also from 1944

https://www.etymonline.com/word/nigra

claimed to be even more derogatory