Where exactly does haitian language come from?

You seem to be asking for a more in-depth answer, which is more than I can answer at this time.
Here are some links on the net:
The National Language of Haiti by Albert Valdman
Istwa lang Kreyòl la
Haitians - Their History and Culture
Haitian Creole ↔ English Reference, Look up Haitian Creole and English Words