Literally, sheaf, or first sheaf of grain, cut during the barley harvest and offered in the Temple on the second day of Passover. No new grain could be eaten before that offering was made. The Bible commands Jews to count seven weeks from the day of the offering of the Omer, a custom which has been preserved to this day (sefirat ha-omer, or counting of the Omer). This 50-day period culminates in the Feast of Weeks (Shavuot, or Pentacost), commemorating the giving of the Torah at Mount Sinai.

Because of misfortunes that have overtaken the Jewish people during this time of year, it has come to be regarded as a period of mourning. For this reason, weddings and other festivities are not celebrated . Especially associated with the sefirah is a plague which broke out among the disciples of Rabbi Akiva during Bar Kokhba‘s uprising which took place in the month of Nisan 135 C.E. Jewish legend tells that the plague subsided on Lag b’Omer (“the 33rd day of Omer”). Therefore marriages may be solemnized on that day which is celebrated outdoors and, in Israel, with pilgrimages to Meron, a town in Galilee.