Q. The Rosh HaShanah morning Kiddush says, “Blow the shofar on the new moon, bakesseh l’yom chaggenu, on our designated festival day”. Is this what bakesseh really means?
A. It is a difficult phrase, coming from Psalm 81.
Applying it to Rosh HaShanah, Samson Raphael Hirsch links it with kisseh, a chair; he quotes Prov. 7:20, which refers to Yom HaKisseh, “The Day of Enthronement”.
Others connect kesseh to a root that means to conceal or cover, since on Rosh HaShanah, the beginning of the month, the moon is scarcely visible.
Homiletically this could also suggest that when the year opens, its direction is mostly hidden from us.