Left-side stone radical — pictograph of a rock under a cliff overhang. The indexing radical, and here perfectly literal: a
碾 is a stone roller, the heavy cylindrical mill once turned over grain on a flat slab. By extension the verb means to crush, grind, pulverise. Same family of mineral-action characters:
磨 to grind,
砸 to smash,
砖 brick.
