There is no such thing. All southerners use the same idioms! They become "southern Black" idioms, when blacks move north and forget their culture.
Poll taxes and literacy tests
negro
It means that something is printed in black ink on white paper - it can also mean that something is plain to see or plainly stated in writing.
She sees every situation in black and white although she knows it is wrong.
they disfranshised blacks by: making them pay to vote, pass a literacy test, and understand the state constitution.