Ruler is generally found in ancient books, and its original meaning is the name of ancient agricultural tools. The main shovel at the lower end of the original farm tools was mounted on the plow, which was similar to today's shovel and plow and was used to turn the soil. It is made of wood first, and then of metal. Plow is a tool for digging soil.
The meaning of the whole word: use the shovel, an ancient production tool, to cultivate the land.
Thank you for your hard work.