Why Blue Moon?

Blue moon first inplanted in my mind was about two years ago when I was watching a BBC TV series named"Pennies from Heaven". The song " Blue Moon" was played in it and I like the song. Today I was listening to the radio on my way to work and the host was saying that there is a very interesting phenomenone that people found. Usually we only have one full moon of a month. But when there are two full moons in a month. They call it Blue Moon. This makes me think of my reason to chose the name. Maybe I will find more intersting things about blue moon in the future.