also: つきこもり
noun
Archaic term for the final day of the lunar month, when the moon is hidden. In modern Japanese, 月末 or 晦日 (みそか) are used instead. The cross-reference 晦・つごもり is a related form.
See also: 晦 (つごもり)
旧暦では、月の最終日を「つきごもり」と呼んだ。
In the old lunar calendar, the last day of the month was called 'tsukigomori'.
From 月 (tsuki, 'moon') + 隠り (komori, 'hiding'), referring to the moonless night at the end of the lunar month. The kanji 晦 carries the meaning 'dark' or 'last day of the month'.