black swan

A calque, equivalent to black +‎ swan. Roman satirist Juvenal wrote in AD 82 of rāra avis in terris nigroque simillima cygno (“a rare bird in the lands, and very like a black swan”), creating a durable metaphor and expression. In the sense “unforeseen event” popularized by Nassim Nicholas Taleb in a 2007 book of the same name.[1]

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black swan (plural black swans)

1. Cygnus atratus, an Australian swan with black plumage. [c. 1700]
2. (figurative) Something believed impossible or not to exist, of which an example is subsequently found.
3. (figurative, also attributive) A rare and hard-to-predict event with major consequences.
   • 2011 March 19, Jeff Sommer, “A Crisis That Markets Can’t Grasp”, in New York Times‎:

     In the face of black swans — also known as fat-tail events, for the way their occurrences are distributed along a probability curve — market pricing may be impossible.

   • 2011 June 29, Azam Ahmed, “New Investment Strategy: Preparing for End Times”, in New York Times‎:

     Worried that Greece could go belly up? So-called black swan funds — named for rare and unexpected events — offer a way to profit in the event of a market collapse.

• (Cygnus atratus): Chenopis atratus

• (Cygnus atratus): Anatidae - family; Anserinae - subfamily; Cygnus - genus

• black swan event
• black swan fallacy
• black swan theory

• rara avis
• tail risk

• black swan on Wikipedia.Wikipedia
• black swan theory on Wikipedia.Wikipedia
• Cygnus atratus on Wikispecies.Wikispecies
• Cygnus atratus on Wikimedia Commons.Wikimedia Commons
• “black swan”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.