blue moon: Idiom Meaning and Origin

What does ‘blue moon’ mean?

Blue moon: A rare event occurring only once in a long while.

Idiom Explorer

Enigmatic Origins

The idiom "blue moon" has multiple meanings and origins.

One meaning of the idiom "blue moon" is that it refers to when a full moon appears twice in the same month. This occurs because a lunar month is about 29.5 days long, slightly shorter than the commonly used Gregorian calendar month which is 30 or 31 days long. This discrepancy allows for two full moons to occasionally occur within the same calendar month. Since the 19th century, these rare occasions have been referred to as "blue moons."

Another meaning of the idiom "blue moon" is that it is used to describe something that is uncommon, special, or rare. This figurative use of the phrase dates back to the early 19th century. The expression "once in a blue moon" became popular for describing events or occurrences that happen very infrequently or are exceptionally rare.

The blue moon is a rare, infrequent occurrence.

The origin of the phrase "blue moon" can be traced back to the Old English word "belewe," which means "betray" or "deceive." In early English, the phrase "belewe moon" was used to describe a long period of time often associated with betrayal or deception. Over time, this expression evolved into the modern-day "blue moon."

The idiom "once in a blue moon" is related to the idiom "blue moon." It is used to describe events or occurrences that happen very infrequently or are exceptionally rare. Both idioms capture the idea of something happening seldomly.

A popular misconception is that the phrase "blue moon" refers to the moon appearing blue in color. However, this is not the case. The term "blue moon" is purely idiomatic and does not have any direct connection to the moon's color.

The idiom "blood moon" is another phrase that is sometimes associated with the idiom "blue moon." A blood moon refers to a lunar eclipse where the moon appears reddish in color. This phenomenon occurs when the Earth passes between the Sun and the Moon, casting a shadow over the Moon and giving it a reddish hue. While the idiom "blood moon" is not directly related to the idiom "blue moon" in terms of meaning, both phrases involve unique lunar events and have captured the interest of people worldwide.

The idiom "blue moon" carries different meanings and origins. It can refer to the occurrence of a second full moon in the same month or describe something that is uncommon or rare. The phrase has ties to Old English and has evolved over time. The idioms "once in a blue moon" and "blue moon" are related in that they both convey the idea of infrequent or rare events. The idiom "blood moon" is not directly connected to the idiom "blue moon" in meaning but shares the theme of extraordinary lunar occurrences. The idioms surrounding the moon continue to intrigue and captivate people's imaginations.

Example usage

1. It's so rare to see my sister cook, but on a blue moon, she might surprise us with a delicious meal.

2. The team hasn't won a championship in decades, but they finally did under a blue moon.

3. I hardly ever go out at night, but once in a blue moon, I'll go to a party with my friends.

More "Time" idioms