The Rebbe:
– The name “Rosh Chodesh” relates to the word “chidush” meaning “novelty” or “new development.” Each month, the moon undergoes a “new birth.” This moment of birth includes the potential for the moon’s subsequent growth.
In this context, we can understand the name Rosh Chodesh, literally, “the head of the month.” Just as each year, on Rosh HaShanah (“head of the year”) “a new light which never shone before” is revealed, similarly, each Rosh Chodesh, a new dimension of this light is revealed in the world.
From the Rebbe’s talk on the 1st Day of Rosh Chodesh Kislev and Shabbat Toldos, 5752(1991).