A colloquialism native to urban areas with a high concentration of ethnic variance, circa 1992. The expression alludes to Casper the Friendly Ghost, and is equivalent to "leaving," "departing," or "goodbye." Tracing the etymology is somewhat difficult, but the earliest recorded instance of this phrase that I could find is from Redman's 1992 album Whut? Thee Album, the song Watch Yo Nuggets (Erick Sermon's verse).

Compare: Audi, Jetting, out like X