Shavuot is a festival with a variety of names, each one representing different aspects of the festival. It is the Hag HaKatzir (harvest festival), Hag HaShavuot (festival of weeks) and Hag Habikkurim (festival of first fruits). The Torah describes the biblical festival in all three ways. For example, in Numbers 28:26, the people are commanded to offer a new meal-offering to the Eternal on the "day of first fruits" in the festival of weeks.
The name "Atzeret" ("cessation" or "solemn assembly") is used later in the Talmud to reflect how the rabbinic sages viewed the festival as a conclusion to Passover and the subsequent counting period of the omer (when the sheaf offerings were given in the Temple and each of the 49 days is counted). The talmudic rabbis also added the name "zeman matan torateynu" (time of the reception of Torah), which reflected their view of the festival as also having been the time in history when the Jews received the Torah on Mount Sinai. In post-Talmudic times, the name "Shavuot" came back into use.
The counting period which began during Passover and lasted seven weeks--a week of weeks--marked the period from the harvesting of barley to the harvesting of wheat (the "first fruits" of the wheat harvest)--the last cereal to ripen--on Shavuot. In Deuteronomy 16:11 it is referred to as a festival of rejoicing. In Exodus 34:22, the people are commanded to make a festival of weeks with the first offering of the wheat harvest. The offerings are not given. However, in Leviticus 23:17, there is a prescribed offering of first-fruit loaves of new meal of two-tenths of an ephah (a biblical measurement), baked with leaven. The loaves were to be waved in the Temple.