I am not sure if the question even belongs here. Please correct me if it is out of context.
Usually, we say that $K^L(s)$ is a controller over the plat $G(s)$. Is there any reason it is called a plat?
The controlled system may be a car with cruise control, an actual plant, or even the famous F15. These are not necessarily plants. Was the theory originating from real plants and factories?
I am looking for something anchored in resources and not an intuitive explanation.