This comes from the streets, man! Often referred to in rap songs. It indicates the need to have the gangsters "up" or on top of things, and keep the Ho's (
bitches) down. Thought to have originated from pimps who would say it to indicate their whores were on their backs making the
money for the pimps. Often said when greeting a fellow G, or upon entering a room or
party. Meant to re-assure