What is Hiraniku in Japanese Katana terminology?

The term "Hiraniku" (平肉, ひらにく) refers to the thickness of the body of a Japanese sword. It is a term used to express the sense of volume or thickness of the sword. When a sword is made thick, it is often described as "Hiraniku tappuri" (plenty of Hiraniku). The term "Habaniku" refers to the thickness on the blade side, while "Jiniku" refers to the thickness on the flat side. The overall thickness, including both Habaniku and Jiniku, is referred to as "Hiraniku". A sword with a thick body is described as "Hiraniku tsuku", while a sword that has been worn down by polishing or originally made thin is described as "Hiraniku kareru".