Sometimes 'as hard to know as dark' and 'as immovable as the mountain' are written in a different order depending on the version of the book, and it is thought that 'Fu-Rin-Ka-Zan' were taken from the first four phrases in one of those books.
各版本によっては「難知如陰」と「不動如山」が逆に記されている場合もあり、「風林火山」はそうした版の前四句を採用したものと思われる。