Miller - person who produces flour or other products by operating a mill

"A miller is a person who operates a mill, a machine to grind a grain to make flour. Milling is among the oldest of human occupations. "Miller", "Milne", and other variants are common surnames, as are their equivalents in other languages around the world. Milling existed in hunter-gatherer communities, and later millers were important to the development of agriculture. - Wikipedia"