What is meaning of Nigeria? Many people would say it is Niger Area. Fans of Flora Lugard nee Shaw I dey hail una................

But what is meaning of word 'Niger'? Some would say it is derived from River Niger.

From my research which would benefit other is: the word Niger is derived from Latin word Nigrum. The nigrum is a parent word for Negro or Nigger in modern America slang.

from Latin nigrum (nominative niger) meaning "black, dark, sable, dusky,".

No wonder, Nigeria is the most populous black people on earth.
Now my definition of Nigeria is the country with the largest persons on earth.

Because I want to learn, please I want researched definition.