it's a latin word, not a greek one
"member of a black-skinned race of Africa," 1550s, from Spanish or Portuguese negro "black," from Latin nigrum (nominative niger) "black, dark, sable, dusky,"
it's pretty unclear in linguistic history when greek and latin had significant bearing on one another, i wouldn't say latin has origins in classical greek at all, greek is not even an italic language
the two languages (greek and latin) existed in parts of the italian peninsula, with greek in the south and latin in central italy (or what we now call italy).
so yeah breh, back to the drawing board. your theory doesn't stand up