So I'm reading a book set in the American South in the beginning of the 1900 and I stumble upon the use of the verb is with you ("you is", "is you?") in conversations: eg. "is you Samson Fuller?". I've heard this in rap songs before, but this usage made me wonder how it came about. Could someone give any insight into this? History, usage today?
(The writer also adds an s to some verbs, eg. "I doubts that", "I sees", etc. What's with that?)