Full Corn Moon or Harvest Moon
For millennia, people across Europe, as well as Native American tribes, named the months after features they associated with the Northern Hemisphere seasons, and many of these names are very similar or identical.
Full Moon Names
Today, we use many of these ancient month names as Full Moon names. A common explanation is that Colonial Americans adopted many of the Native American names and incorporated them into the modern calendar.
However, it seems that it is a combination of Native American, Anglo-Saxon, and Germanic month names which gave birth to the names commonly used for the Full Moon today.
Harvest Moon Most Years
Most years, the September Full Moon is the Harvest Moon. This particular name is given to the Full Moon which is closest to the September equinox, which is the start of fall in astronomy. The astronomical seasons do not match up with the lunar month. Therefore, the month of the Harvest Moon varies. Usually, it occurs in September, but every three years, it is in the month of October.
However, the September Full Moon also has traditional given names; the most well-known one is the Full Corn Moon, or simply Corn Moon. Another name is Barley Moon, but this name is also used for the August Full Moon. These names all refer to crops which are harvested in the early fall.