The Phrase in Question

The only thing that can get me out of my cold prickly slump is a Wordy Wednesday. Let’s try an installment of "The Phrase in Question" on for size today.

Once in a Blue Moon

Meaning: Happens on rare occasions; not common.
Example: I’ll have a hankering to watch a science fiction movie once in a blue moon.
Provenance: Several - see below

• Most commonly, a blue moon means: the second full moon that fall in the same calendar month. It is very rare for a blue moon to occur – they only happen about once every 2 ½ years, hence the phrase.
  
• Dating back further to the 1800s, the Maine Farmers Almanac, and the Christian Ecclesiastical Calendar, a blue moon can also mean the third moon in a season that has four full moons. Each month has a full moon making a grand total of 12 moons a year, but some years there are thirteen moons causing one season to have an extra (4th) moon. The third moon is called the "blue moon." It was important for the Ecclesiastical calendar that they keep track of the extra moon so they could "skip it" in their worship calendar. Otherwise, everything would get off track.
  
• The trend of calling the moon blue dates back to a 1528 proverb. "If they say the moon is blue,We must believe that it is true." Apparently, it meant that something was absurd because it’s absurd to call the moon blue, or something…This excites me not at all, but it might strike someone’s fancy.
  
• On occasion, the moon has appeared blue to sky gazers because of volcanic eruptions or forest fires. According to the website, The key to a blue moon is having in the air lots of particles slightly wider than the wavelength of red light (0.7 micron)--and no other sizes present. This is rare, but can happen (1883 Indonesian volcano Krakatoa eruption). To read more about this phenomenon, go here.

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