Full moon names date back to Native Americans, of what is now the northern and eastern United States. The tribes kept track of the seasons by giving distinctive names to each recurring full moon. Their names were applied to the entire month in which each occurred. There was some variation in the moon names, but in general, the same ones were current throughout the Algonquin tribes from New England to Lake Superior.
This August, there will be a second full moon on August 31st. This is rare, thus the name for the second full moon of the month - Blue Moon. So, the term "Once in a Blue Moon" is actually an accurate statement.
This photo was taken from the Lakewalk at 8:35PM last evening as the moon drifted behind the North Pier Lighthouse.