The five zang-fu organs are yin, the sun is yang and the moon is yin, so the five zang-fu organs are beside the moon. In addition, the word "moon" used to mean meat, and things on people are naturally made of meat. The moon originally means meat, so often some Chinese characters representing the body are next to the word moon, such as muscles and abdomen, including what you said. Next to the word "moon" is the deformation of Oracle Bone Inscriptions's word "meat", which is actually the word "meat" and is essentially different from the moon.