Run-of-the-mill

Origin

Imagine the rhythmic clatter of a 19th-century mill, where grain poured down chutes, ground, and then churned out as flour. The "run of the mill" was simply whatever came off the production line—the standard, undifferentiated product before any sifting, grading, or special selection. It was the average, the ordinary, the bulk yield. This industrial imagery of uniform output before any quality control quickly bled into common language. It became a vivid shorthand for anything lacking distinction or flair, anything just 'average,' much like the sacks of flour all looking much the same as they left the mill.