Originated in the Central American country of Belize as part of the kriol (creole)(broken English) language spoken there.
Dan: "Gimme some a yo coke, mi bally"
Tony taking a look at the pint seeing bread crumbs floating around in the coke
Tony: "Buay, i no tink u want drink some a mi wash-back weh di inya"
Dan: "Let me have some of your soda, pal."
Tony: "I don't think you want to drink from my soda with wash-back food particles floating around in here."