Gracie Films is the production company behind The Simpsons, and its closing logo is the source of this shush. Viewers heard the brief sound at the end of episode after episode, which made it familiar long before short-form video existed. As clips from television logos began circulating on soundboards and in edits, the shush was lifted out of its original context and reused as a quick way to demand quiet. It endures because it is short, instantly understood and tied to a show many viewers recognise, so a single second can set up a joke without explanation.