Stone Milling Idioms (We Say Them All the Time!)
Grist for one's mill ~ Since wheat and corn are ground by 'teeth,' the grinding stones 'chew' the grist into flour; thus to 'chew' over something became a thought or idea to ponder. The daily grind ~ The repetitive nature of milling led to the concept of 'the daily (same old) grind.'. Run of the mill ~ The ordinary, daily grind.