Once in a blue moon

Origin of Phrases - O

Once in a blue moon

Meaning: To happen only on rare occasions.

Example: The Post Office regularly fails to deliver checks sent in payment to me, but bills sent to me fail to be delivered only once in a blue moon.

Origin: Two full moons in the same month are extremely rare, though they do happen. A second full moon has come to be called a blue moon. This is apparently because the Maine Farmers Almanac used to list the date of first moon in red text, and the second moon in blue.

The first published use of the phrase was in the 1600's, "Rede Me and Be Not Wrothe" and English poem by Roy and Barlow that in part says "If they say the moon is blue, we must believe it is true" the "they" in this poem referring to English nobility.

Also, the moon on rare occasions actually appears to be blue. For example, if there was a volcanic eruption somewhere, suspended ashes in the atmosphere can make the moon appear bluish.

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