Derived from the trade of carpentry, a millwright originally was a specialised carpenter who was trained as a carpenter and as well had working knowledge of gear ratios, driveshaft speeds, and other equations. The "mill" in millwright refers to the genesis of the trade in flour mills.
A millwright today is someone who maintains or constructs industrial machinery such as that which would be related to assembly lines, also pumps, valves, printing presses, etc.
