Switching to blue moon, here's something:
What Is a "Blue Moon?"

Usually, a moon's cycle lasts 29 1/2 days, called the moon's synodic period. During the months of the year, excepting February, it is possible that a full moon could appear twice. When this rare occurence happens, about once every two to three years, it is called a "blue moon."

The expression "blue moon" dates back to the time of Shakespeare. If someone said, "He would argue the moon was blue," the average sixteenth century man would take it the way we understand, "He'd argue that black is white."*** This meant that a blue moon was something absurd, which led eventually to a second meaning, that of "never." To say that something would happen when the moon turned blue was like saying that it wouldn't likely happen.

In the 1940's, astrologists and meteorologists started using the term to describe when the moon takes on a blue coloration. This happens when small atmospheric particles interfere with light, causing a bluish tint to the moon's appearance from earth. The particles can come from things such as forest fires and volcanic eruptions. However, this only occurs "once in a blue moon."
From: Kentucky Department for Libraries and Archives

I was trying to find a site where you could listen to the song Blue Moon of Kentucky, but the link here doesn't work. But YouTube has a clip of the Father of Bluegrass, Bill Monroe, doing it. He wrote it in '46 or '47.
Bill Monroe