Japanese people like to recognize relatives, respect (on the surface or in the bones) is called forward, and contempt is called backward. This is basically what China and South Korea now call "honorific words". Eunuchs with high status have a very high authority in the palace and a long history (there are many eunuchs after Qin Dynasty and Han Dynasty), because the advanced title of "Ye" has always been used by some serious nobles, and eunuchs are actually despised. It is impossible to use the same honorific words as those nobles called "ye" to show that they have high authority over eunuchs, so a similar word is used.