Q. Why is the month of the High Holydays called Tishri?
A. The Biblical name is Etanim (1 Kings 8:12) which means “strength”, because it is a time for harvesting one’s strength, the crops; or “flowing water”, because it is the month of the early rains (Deut. 11:14).
Homiletically, this name may refer to the powerful mitzvot associated with the month (RH 11a) or to the mighty patriarchs, Abraham and Jacob, who were born in this month (Maharsha).
The Babylonian name Tishri was adopted during the exile in Babylon. It possibly comes from a root shari, which has a number of meanings – “to begin”, since the Creation of the world is held to have been in this month; “to loosen”, because this is the month when the power of sin is loosened; and “to be straight”, since human lives return to the straight path during Tishri.
There is a rabbinic theory that the letters of B’reshit (“in the beginning”) can be re-arranged to form B’Tishri, alluding to the belief that this was the month of the Creation.