Does "six books" refer to six books?

The word "Liushu" first appeared in "Zhou Li · Di Guan", but there is no detailed name of "Liushu" and no explanation of "Liushu.". The earliest interpretation of the six books appeared in the Western Han Dynasty Liu Xin's "Qi Lue", and the Eastern Han Dynasty Xu Shen gave a formal definition of the "six books" in "Shuowen Jiezi · Xu". The interpretation of the "Six Books" by later generations is based on Xu Shen's theory. The so-called "six books" refer to the six character-making methods of referring to things, pictographic, pictophonetic, associative, Zhuanzhu and phonetic loan. Strictly speaking, only the first four of them are character-making methods, because Zhuanzhu and phonetic loan involve the use of characters and do not create new characters. Concretely speaking, referring to things and pictographs belong to the single-body character-making method. Pictographs are the most primitive character-making method, that is, using pictures to represent things. In the process of the evolution of characters, the pictoriality gradually weakens, while the symbolism gradually strengthens. Pictographic characters have great limitations, because some of the more abstract meaning is difficult to be expressed in pictures, which is supplemented by the method of referring to things. Compared with pictographic characters, the abstract meaning of referring to things is stronger and has more significant symbolic characteristics. Pictophonetic characters are composed of pictophonetic radicals (also called "meaning symbols") and phonetic radicals (also called "notes"). The pictophonetic radicals represent the meaning or category of the characters, while the phonetic radicals represent the pronunciation of the characters. Associative characters are composed of two or more single characters, and several glyphs express the meaning of the character together. Some associative characters also have the characteristics of tangible phonetic characters, and the two are not completely separated. Zhuanzhu and phonetic loan are the methods of using characters. Phonetic loan refers to the phenomenon of homophonic substitution, that is to say, some languages do not have characters corresponding to them, so they should find the same pronunciation to write. Different scholars have different views on Zhuanzhu, which can be summed up as three explanations: form change, meaning change and sound change, but no matter what the actual meaning is, Zhuanzhu produces the phenomenon of multi-word synonymy, and correspondingly, loan produces the phenomenon of polysemy.