To Be Smart = Not a Nigger
To Be Nigger = Not Smart
A fictional term at best!
However as a slang term "Smart Nigger" is a term meaning
NOT acting smart or intelligently.
Joe: Did you see the news about the Nigger who robbed the
bank and forgot to grab the money when he ran out.
Max: Yea, ... he sure is a "Smart Nigger" ain't he?