When pigs fly


The phrase "when pigs fly" is an adynaton—a figure of speech so hyperbolic that it describes an impossibility. The implication of such a phrase is that the circumstances in question will never occur. The phrase has been used in various forms since the 1600s as a sarcastic remark.

Meaning

"When pigs fly" is an adynaton, a way of saying that something will never happen. The phrase is often used for humorous effect, to scoff at over-ambition. There are numerous variations on the theme; when an individual with a reputation for failure finally succeeds, onlookers may sarcastically claim to see a flying pig. Other variations on the phrase include "And pigs will fly", this one in retort to an outlandish statement.
An example occurs in the film The Eagle Has Landed: an Irish secret agent working for the Nazis replies to a German general speaking of Germany's shortly winning World War II, "Pigs may fly, General, but I doubt it!" Later, when the Irishman sees German soldiers parachuting before an attack, he says to himself, "Mother of God! Flying pigs!"
An identical phrase, used to express impossibilities, exists in Romanian, Când o zbura porcul, literally meaning "When the pig shall fly"; an equivalent also implying an animal is La Paștele cailor, literally: "on horses' Easter". Similar phrases in English include ":Wiktionary:when Hell freezes over|when hell freezes over", the Latin expression "to the Greek calends", and "and monkeys might fly out of my butt", popularized in Wayne's World skits and movies. They are examples of adynata. In Finnish, the expression "kun lehmät lentävät" is used because of its alliteration. In French, the most common expression is "quand les poules auront des dents". In medieval Hebrew manuscripts, the expression "until the donkey ascends the ladder" is attested.
The idiom is apparently derived from a centuries-old Scottish proverb, though some other references to pigs flying or pigs with wings are more famous. At least one appears in the works of Lewis Carroll:
American literature author John Steinbeck was told by his professor that he would be an author when pigs flew. When he eventually became a novelist, he started to print every book he wrote with the insignia "Ad astra per alas porci". He sometimes added an image of a flying pig, called "Pigasus".
Incidentally, a pig finally flew 4th November 1909, when John Moore-Brabazon, 1st Baron Brabazon of Tara took a small pig with him on board an aeroplane.

In popular culture