a group of (sometimes stupid) people that make comments on something they are watching or listening to; spectators with a verbal opinion
Howdy Doody, a show that started in the 1940's (not 50's), the children in the crowd were considered the "Peanut Gallery."
Announcer: No more comments from the peanut gallery!!!!!!
Vaudeville era woman: Throw more nuts chap!!!!
Vaudeville era man: I'll give you some of my nuts instead..