Just for the fun of it...
"Kou", "Otsu", "Hei", "Tei"... are chinese characters originally used to designate the celestial system in the ancient lunar calender. In Chinese it is pronounced "Chia", "Ii", "Bing", "Cheng", and in Korean, "Gab", "Eul", "Byung", "Jung"...
After a while, Asian people began using these letters when giving order to a certain sequence of things... so it roughly corresponds to the Western method of designation - "Alpha.. Bravo... Charlie.. Delta.." or "Anton.. Bertha.. Cesar.. Dora..." etc etc.. When Westerners go A, B, C, D.... Japanese go Kou, Otsu, Hei, Tei.. etc etc..