Why is the close looped model under control called plant? I am not sure if the question even belongs here. Please correct me if it is out of context. 

Consider a closed feedback loop.


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.
I have heard that the word comes from &quot;plant&quot; as in &quot;steam plant&quot;.  But I don't know of any historical research that's been done to pin down the term.
I did just check my copy of &quot;On Governors&quot; by James Clerk Maxwell himself (that guy got around).  At least in 1868, Maxwell wasn't using the word &quot;plant&quot; for &quot;thing being controlled&quot;.