Possibly related to H3680 (kasah, 'to cover/conceal') referring to the moon's full covered-face appearance, or from a root meaning 'plumpness.' Kese refers specifically to the full moon or the feast held at the full moon.
The full moon was a sacred marker in Israel's liturgical calendar. Psalm 81:3 commands, 'Blow the trumpet at the new moon, at the full moon, on our feast day.' The kese marked the midpoint of the month, corresponding to feasts like Passover (14th of Nisan) and Tabernacles (15th of Tishri). These feasts, held at full moon when the night was brightest, carried rich symbolism: the full revelation of God's light, the completeness of His provision, the fullness of His covenant celebrations. Creation's lights were given for 'signs and seasons' β the moon's cycle structured Israel's worship life.