mid-15c., "act or business of grinding (grain) in a mill," verbal noun from mill (v.1). In reference to shaping metals by 1610s; in coin-making by 1817.
Entries linking to milling
mill v.1
1550s, "subject to mechanical operations carried on in a mill;" 1560s, "to grind in or as in a mill, reduce to fine particles;" from mill (n.1). Meaning "to flute the edge (of a coin, etc.) is from 1724. Related: milled; milling.