Because, he was a truth speaker during the old days when we had separate laws for The colored and uncolored. Selma is a feminine name of ambiguous origin. It could be a form of Selima, which in turn is a name first recorded in a poem by Thomas Gray (died 1771). One possibility is that Selima was influenced by the Arabic name Selim meaning "peaceful". And so because of that it’s name Selma. (Might not be right.)