Have no idea. Slang changes from generation to generation. I drive a school bus, and one of my black students, says "later dog" when he got off the bus to me. I was pissed. When I was growing up calling a woman a dog, meant, she was ugly. His friend later told me it was meant as a compliment. because dogs are loyal, and your friend. hell, I was realy confused then. I didnt know, if he was covering up for his friend or if it was true.
Non of those, it`s a cry from the heart for his real mama whom he sees in you. Best compliment ever!
Watch "count blackula" and decide for yourself.
it usually means he find you to be unbearably unattractive and he is pleading for your "mama" to open the vaginal canal and return you to where you came from.