When a full moon that is normally seen once every month is seen again at the end of the month, it is called a blue moon. It is said that you can see a blue moon about once every 2.7 years. Why is it expressed as blue although the color of the full moon is not actually blue? Think that it might be chosen as blue due to its color of the earth which is rare biosphere in the universe. Besides, seeing at the end of the month seems to mean that you see it like fate when you almost give up. So, 'Once in a blue moon' is a rhetorical expression used in very rare cases.
Yue Lao (Chinese: 月下老人; pinyin: Yuè Xià Lǎorén; lit. 'old man under the moon') is a god of marriage and love in Chinese mythology. He appears as an old man under the moon. Yue Xia Laoren sign in Chinese, English, and Japanese. TaipeibYue Lao appears at night and "unites with a silken cord all predestined couples, after which nothing can prevent their union." He is immortal and is said to live either in the moon or in the "obscure regions" (Yue ming), the Chinese equivalent of Hades. His legends serve as the basis for the Red thread of fate. Yue Lao
There is a romantic word, what they call old man under the moon as matchmaker. Oops! also related with Moon. Too many remakes by legendary artist as bellow.
Boswell Sisters | Billie Holiday | Elvis Presley | Nat King Cole | Frank Sinatra | Rod Stewart | Ella Fitzgerald | Dean Martin
Remake
That's what I live for | Million of red roses | We're alone | Last kiss | I'll be missing you | Run To You | After the love has gone | Champion | Stay | Earth angel | In My little Corner of the World | Greatest love of all | You Can't Hurry love | Sad Café | Come rain or Come Shine | Be my baby | Sound of Silence | Everybody changes | Blue Moon