In the Mishna and in the Talmud the festival of Shavuot is called Atzeret. What is the meaning of this name and why was the festival called so? A variety of views have been expressed on that subject.
More than one hundred years ago, the Hebrew writer Kalman Schulman suggested what might well be the correct interpretation.
Writing about Atzeret in the Hebrew periodical HaTzefira (1879, no. 26), he stated that the Torah itself gave that name to the day of the festival not only once but three times! Three times the Torah calls the day of the giving of the Torah “day of assembly” (Yom HaKahal). “The L-rd gave me the two-stone tablets…. Upon them were written all the words that the L-rd spoke to you on the mountain out of the fire on the Day of Assembly” (Devarim 9:10). “He wrote on the tablets.. which the L-rd spoke to you out of the fire on the Day of Assembly” (ibid. 10:4). “According to all that you asked from the L-rd your G-d on Horev on the Day of Assembly (ibid. 18:16). Atzeret means assembly; as a name for Shavuot, it is another word for Yom HaKahal (Day of Assembly), used by the Torah for the day of the giving of the Torah.
Schulman added that he hoped that his interpretation would be well received. “If indeed, no one preceded me with this explanation, I would be happy in the knowledge to have been the first to suggest it,” he wrote.
I would like to note that Schulman was not the only one in his time to offer the above explanation. The same explanation of Atzeret, based on the same three verses is found in Rabbi Yaakov Tzvi Meklenburg’s HaKetav VeHakabbala (on Devarim 9:10).
However, it is possible that Schulman’s article appeared in print before Rabbi Mecklenburg’s interpretation was published. Rabbi Meklenburg died in 1865. The first edition of his HaKetavVeHaKabbala appeared in 1839. It was reprinted twice during R. Meklenburg’s lifetime with his additions. In 1880 Abraham Berliner published a new edition with additional material from manuscripts left behind by the author. The above mentioned interpretation of Atzeret is not in the first edition. It is found in the fourth edition, which as mentioned earlier appeared in 1880, i.e. about one year after the publications of Schulman’s article. The second and third editions were not available to me and I do not know whether the interpretation of Atzeret is included in them.
Moreover, the above mentioned interpretation of Atzeret has already been offered by an early commentary on the Torah, written by Rabbi Menachem R. Shlomo, who lived in the twelfth century, probably in Italy. R. Shlomo Buber published his commentary on Bereshit and Shemot and some fragments of his commentary of VaYikra from manuscripts (Berlin 1900-1901). The remainder has been lost but quotations from the commentary have been preserved in the works of some early authorities. (Rishonim). R. Buber collected these quotations and published them in the introduction to his edition of the commentary.
One quotation (which originally appeared in the commentary on Parashat Pinhas) reads as follows: Why is the festival of Shavuot called Atzeret? Because they were then assembled before the L-rd, on the Day of Assembly, on the sixth of Sivan…. because Moshe Rabbenu called it Yom HaKahal (Day of Assembly) our sages named it Yom Atzeret. Compare Kiru Atzara (Joel 1:1) call an assembly.
American Jewish Times
From Rabbi Tovia Preschel, here.