Answer: Walla Walla

In the early days of radio broadcasting, producers discovered that they could easily recreate the murmuring sound of a crowd in a restaurant or other public space by having the actors not currently involved in the dialogue quietly repeat the word “walla” over and over again.

With the advent of television broadcasts wherein the listener-turned-viewer could now see the crowd, they switched to using casual improvised conversation (so that it wouldn’t look like everyone in the restaurant was, oddly, chanting the same thing over and over again). Despite the transition away from using the pat phrase, the term is firmly embedded in Hollywood, and actors who provide the background noise for the post production effect that is layered over the video of the background extras speaking are known as the “walla group”.

What’s particularly interesting about the “walla walla” phenomenon is that the phrases used by actors are highly regional and influenced by the native language of the region. American actors said “walla walla”, British actors said “rhubarb rhubarb”, German actors said “rhabarber rhabarber”, and Japanese actors said “gaya gaya”.