The name Lag B'Omer literally means the 33rd day of the (counting of the) Omer. Lag is not really so much a word but is used here because Lag has a numerical value (gematria) in Hebrew of 33. In Gematria, each hebrew letter is assigned a numerical value and therefore sometimes numerical valued are spelled out in letters forming words.
This is not a Biblical holiday.
This is a one-day minor holiday that is to be celebrated. It is found inside of the 49 days of the counting of the Omer. It is held on day number 33. Lag B'Omer is on the 18th day of the month of Iyar.
There was a famous Rabbi (Akiva) that had a strong following. Those who followed him are referred in literature as disciples or talmudeem, usually taken to mean students of his teachings. Many of these students, possibly as many as 24,000, died due to a sickness similar to the croup (Yevamot 62b). They are believed to have died in between Passover and Shavuot, the period of counting of the omer. The majority holds to the belief that they all died during the first 32 days of the omer counting. That is why day 33 is so special. Tradition has it that there was not death on this day, the plague was over.
It is considered a time of morning for the 32 days that the students died. Because of this, restrictions are in place to keep this from being a happy time. For some, music is forbidden. Some Rabbis will not officiate at a wedding and some Jews will not cut their hair. On the 33rd day of the counting of the Omer, there is a minor holiday (Lag B'Omer) commemorating a break in the plague that killed the students. This is a happy day, and the restrictions that are in place are lifted.
Rabbi Menachem B. Solomon Meiri (died 1306) stated that the tradition of Lag B'Omer had come down from the Geonic period. He mentioned that it was customary not to fast on Lag B'Omer (Commentary on Yevamot 62b). He was thus the first authority to indicate the festive aspect of Lag B'Omer.(1)
In Israel, the holiday is marked most notably with traditional bonfires throughout the country. The bonfires - a tradition kept by Jewish children of all backgrounds in Israel - are said to represent the light of Torah disseminated by Rabbi Shimon and his teacher Rabbi Akiva. Lag B'Omer has also halakhic significance as a cessation in the semi-mourning observances that occur between Passover and Shavuot.(2) There is often a parade of Torah Scrolls that goes from the city of Tzfat to the grave site of Rabbi Shimon. Then some of the celebration officially begins.
There are also many "first haircuts" to three year olds learning the Torah.
The Government recently decided to make Lag BaOmer a national day honoring IDF reserve soldiers, in appreciation for their motivation and willingness to "share the load".(3)Soldiers serving in reserves on this day might receive things like free cellular phone calls and free rides on Israel Railways.
It also marks the anniversary of the death more than 1,800 years ago of Rabbi Shimon Bar Yochai, whose teachings comprise the text of the primary Kabbalah sourcebook, the Zohar (often interpreted as light). Rabbi Yochai became a kind of student of Rabbi Akiva's teachings. In celebration of this holiday, some Jews visit Rabbi Yochai's home town Meron, near Safed in the Galilee.
This holiday is considered by some a festival that also celebrates the downfall of Adolf Hitler.
Adolph Hitler committed suicide on April 30, 1945, at 3:30 p.m. This is also the 17th of Iyar 5705. His body was set on fire in the late afternoon and burned until dusk. The 18th of Iyar which is Lag B'Omer, therefore, marks the end of the Hitler era.(1)
Since the holiday of Lag B'Omer isn't found in the Bible, there is not a direct link between the Messiah and this holiday.
We know that Jesus was crucified on Passover. The second day of Passover is the first day of counting the omer. We also know that the sending of the Holy Spirit came on day 50 of the counting of the omer, also known as Pentecost. Jesus walked the earth in a resurrected body sometime during the counting of the omer. We cannot say for sure exactly where he was on day 33. We do know, however, that this was 17 days before God sent the Holy Spirit.
On the 33rd day (Lag B'Omer), it is common to go to the park and cook out. Perhaps a picnic with some kosher hot dogs would be a good opportunity for fellowship.
For a list of future holidays dates check the Master Calendar Table.
Learn more about how this holiday is linked to the holiday of Counting Of The Omer.
Coinciding with Lag B'Omer is the annual Ghriba pilgrimage on the Tunisian island of Djerba. Thousands of French and Italian Jews as well as Tunisian-born Israelites descend on the town, home of the El Ghriba synagogue, the oldest known Jewish house of worship in Africa. The name of the synagogue means "marvelous" or "strange," based on several traditions, one of which is that Jewish priests fled there after the destruction of the First Temple.(4)
1). Information from The Biblical And Historical Background Of The Jewish Holy Days, by Abraham P. Bloch is copyrighted material and was used with permission of the publisher. KTAV Publishing, 900 Jefferson Street. Box 6249, Hoboken, NJ 07030-0102
2). Arutz-7 News: Monday, May 19, 2003
3). Arutz-7 News: Monday, May 15, 2006
4). Arutz 7 News.