A miller usually refers to a person who operates a mill, a machine to grind a cereal crop 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 ('Möller' or 'Mueller' in German, 'Molinari' in Italian etc.).
Milling existed in hunter gatherer communities, and later millers were important to the development of agriculture.
The materials ground by millers are often foodstuffs and particularly grain. The physical grinding of the food allows for the easier digestion of its nutrients and saves wear on the teeth.
Non-food substances needed in a fine, powdered form, such as building materials, may be processed by a miller.
From: 'Wikipedia: Miller'
The Ordinary of this society, dated September 20th 1578, citing another older date, constituted twenty free millers a fellowship, with perpetual succession, and enjoined them to choose two wardens every year, on the Sunday next before St Andrew's day, who might sue and be sued, & c. in the courts of the town; and that when the general plays should be performed, they should play the ancient one of the society, called "Deliverance of the Children of Israel out of Thraldom, Bondage and Servitude of King Pharoh," on pain of forfeiting twenty shillings for absence: that no stranger or alien born should be taken apprentice, or set to work, on pain of 6s. 8d.; and that apprentices should serve seven years: that no corn should be ground on Sundays; that each miller in the counties of Northumberland or Durham, who bought corn from Newcastle market, should pay them an acknowledgement of 6d. per annum, and pay 2s. 6d, every time he should be found in the wheat or milk market before two o'clock in the afternoon on market days, unless to fetch away corn which his customers had bought there; and that none such foreign millers should buy corn there, under a penalty of 2s. 6d. for each default.
It further enjoined, that the wardens of this society should make oath in the town-chamber concerning the fines, half whereof to go to the support of the Newcastle part of Tyne Bridge.
In April 8th 1762, a singular order occurs in the books of this fraternity, that if any brother should attend the burial of another with a black hat, he should be fines 6d. for every such default. They have no hall, but hold their meetings at a tavern.
Capt. R. C. Shipley
6 Astley Drive