It was first seen in Oracle Bone Inscriptions's Shang Dynasty. The basic meaning of "Fa" is a kind of artificially cultivated poisonous insect in legend, which is specially used to harm people, such as bewitch, and is extended to parasites in people's stomachs and things that poison people, such as poison.
In daily use, "method" is also often used as a noun, indicating a mental disorder, such as method disease. In people's minds, the word "ancient" has begun to have a negative and concrete image, which makes people who don't know the truth feel inexplicable fear.