Omisoka - New Year's Eve in Japan

December 31 is called "Omisoka" in Japanese.　"O" means " Big" or "Great" and it is used when emphasizing something. In old Japanese language,　"Miso" simply meant "30th"　just like 30 years old is called "misoji". Ｉ speculate that "Misoka" originally meant "30th day of the month". Then the word somehow started to mean "the end of the month".　December 31 is the very end of all months of the year as well as the end of the month. That is why it is called Omisoka, I believe.