Words such as "dollar" and "evil gold" come from pre-Qin ancient books, such as Guoyu. Some scholars believe: "Before iron is smelted into steel, the quality of iron can't catch up with bronze.

Test and analysis: the so-called' evil gold' is iron. Iron can't be used as raw material for advanced weapons before it is smelted into steel. Combined with the times when words such as "American dollar" and "evil gold" appeared, it is not difficult to think of the widespread use of iron farm tools.