The always reliable (cough) Wikipedia, she say:
Southron is a term meaning "a person from the south". It is uncommon in modern usage. It was originally used by
Scots to refer to the
English. Other notable uses are:
A person from the
Southern United States in general
Historically, a person from the
Confederate States of America
A member of the
Haradrim, a human people in the fiction of J. R. R. Tolkien
Anyone who lives below "The Neck" in the series
A Song of Ice and Fire by author George R.R. Martin