Once in a Blue Moon: Definition, Meaning, and Origin

Last Updated on
December 28, 2023

"Once in a blue moon" is a popular idiom used to describe an event that happens very infrequently. It's often used to emphasize the rarity of an occurrence, suggesting that it might happen only once in a great while, similar to the rarity of a blue moon in the night sky.

In short:

  • "Once in a blue moon" means an event is very rare.

What Does "Once in a Blue Moon" Mean?

The phrase "once in a blue moon" refers to an event that occurs very infrequently. The term 'blue moon' is used metaphorically in this idiom to signify rarity, as an actual blue moon—a second full moon in a single calendar month—is rare. For example, someone might say, "I only go to the cinema once in a blue moon," meaning they seldom go to the movies.

Here are some important aspects of this idiom's meaning:

  • It refers to uncommon events not part of a regular schedule.
  • It can also imply something is so rare that it might only happen once in a lifetime.

Where Does "Once in a Blue Moon" Come From?

The term “blue moon” has existed for over 400 years, but its calendrical meaning has only become widespread in the last 25 years. The earliest uses of the term were similar to saying the Moon is made of green cheese, both being obvious absurdities.

The concept that a Blue Moon was absurd eventually led to a second meaning, “never.” For example, the statement “I’ll marry you, m’lady, when the Moon is blue!” would not have been taken as a betrothal in the 18th century.

10 Examples of "Once in a Blue Moon" in Sentences

Here are ten ways you might hear "once in a blue moon" used in everyday conversation:

  • He only visits once in a blue moon; I wish it were more often.
  • She buys a lottery ticket once in a blue moon, not expecting to win.
  • Once in a blue moon, you might find that perfect parking spot right in front of the store, it is what it is.
  • I only eat junk food once in a blue moon; all in all, I prefer to keep a healthy diet.
  • Once in a blue moon, you'll see a meteor shower that takes your breath away.
  • Quite frankly, our team only wins once in a blue moon, but it's very exciting when we do!
  • Once in a blue moon, a movie comes along that changes the way you think.
  • We have a once-in-a-blue-moon sale with incredible discounts.
  • My grandmother says she only feels her age once in a blue moon.
  • Once in a blue moon, we'll have a day off that coincides with perfect weather.

Examples of "Once in a Blue Moon" in Pop Culture

The phrase "once in a blue moon" is quite common in pop culture and is often used to emphasize the rarity or infrequency of an event.

Here are some examples:

  • The famous Irish musician Van Morrison has a song called "Once in a Blue Moon," where he sings about happiness that comes along once in a while.
  • The standard ballad "Blue Moon" has been covered by many artists, including Frank Sinatra, Elvis Presley, and The Marcels. It speaks to the rarity of true love.
  • The poet W.H. Auden wrote about how rare it is for dreams to come true: "Once in a while the dream comes true, and the whole pattern of life is altered, once in a while the moon turns blue."

These pop culture references are a testament to the popularity of the phrase "once in a blue moon" and its relatability.

Synonyms: Other/Different Ways to Say "Once in a Blue Moon"

While "once in a blue moon" is a colorful way to express rarity, there are other phrases and words that can convey a similar meaning.

Here are some alternatives:

  • Very seldom
  • Almost never
  • Rarely
  • On rare occasions
  • Infrequently
  • Not often
  • Every now and then
  • Every once in a while
  • Scarcely
  • Hardly ever

These synonyms can be used interchangeably with "once in a blue moon" to add variety to speech or writing.

10 Frequently Asked Questions About "Once in a Blue Moon":

  • What exactly does "once in a blue moon" mean?

It means something happens very rarely, similar to the rarity of having two full moons in a single calendar month.

  • How did the idiom "once in a blue moon" originate?

The idiom originated from the astronomical phenomenon where a second full moon appears in a single calendar month, which is a rare event.

  • Is a blue moon actually blue in color?

No, a blue moon is not blue in color. The term "blue moon" is based on rarity, not color.

  • Can "once in a blue moon" be used in formal writing?

Yes, while it's idiomatic, it can be used in formal writing to convey the rarity of an event.

  • Are there any songs titled "Once in a Blue Moon"?

Yes, there are songs with that title, reflecting the idiom's popularity in culture.

  • What is the scientific explanation for a blue moon?

A blue moon is a term used in astronomy when there are two full moons in one calendar month, an event that typically happens every two to three years.

  • Does the phrase "once in a blue moon" appear in literature?

Yes, the phrase has been used in literature to emphasize the infrequency of an event or action.

  • Are there any common misinterpretations of "once in a blue moon"?

Some may mistakenly think it refers to something that never happens, when it actually means something that happens very rarely.

  • Is "once in a blue moon" used in other languages?

Many languages have their own equivalent phrases to express rarity, though they may not use the same lunar imagery.

  • How can I use "once in a blue moon" in a sentence?

You can use it to describe an event that occurs infrequently, such as "I only treat myself to a spa day once in a blue moon."

Final Thoughts About "Once in a Blue Moon"

The idiom "once in a blue moon" is a whimsical way to describe something that rarely happens. It's a phrase that captures the imagination and conveys a sense of rarity and specialness. Here's a quick recap of what we've covered:

  • The phrase means an event is very rare.
  • It originated from an astronomical event where two full moons appear in one calendar month.
  • There are many ways to use this phrase in everyday language to express the rarity of an occurrence.

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