The title refers to a colloquialism, in the feminine form, for a courier who delivers money or other valuables of an illicit sort.
During the tape briefing scene at the gas station, Mr. Phelps is shown framed through an automobile tire, in a direct imitation of the way he is always framed in a tilted letter "O" in the opening credits.
Barney passed by the storefront called Landis Department store, which is an iconic presence in the Larchmont Village section of Los Angeles. It shut down in the last decade at the close of the twentieth century. It still has a a smaller footprint in the neighborhood, but it is a shadow of its former self.