What does "Doku" mean ?
Do you know what does "Doku" mean ? As you know, sudoku is Japanese word. It is interpreted as "Su-Doku". Su means a number, and Doku means alone. The rule of sudoku puzzle has digits can not repeat in each row, column and block. Japanese has been explained "alone number" it.
The axiom of Umekichi use all chess pieces. Of course, piece of kNight, too. The capturing move of kNight is not on row, column. It does't mean alone. Therefore, we thought that "Doku" is not suitable to the name of the axiom Umekichi. This is the reason why we didn't use "Doku" for naming.