A Rare Bird

The Black Swan shot to prominence due to Nicholas Taleb to describe events whose probability is low that they are almost unlikely to happen and who have a profound impact.  In English, when the phrase was coined, the black swan was presumed not to exist. The importance of the simile lies in its analogy to the fragility of any system of thought. 

 

 

Here is the Black Swan 

"rara avis in terris nigroque simillima cygno" 

("a rare bird in the lands, very much like a black swan")