Adapted 1 July 2011 while in ceremony

Excerpted from Black Swan theory Wikipedia page:

The phrase "black swan" derives from a Latin expression; its oldest known occurrence is the poet Juvenal's characterization of something being "rara avis in terris nigroque simillima cygno" ("a rare bird in the lands, very much like a black swan"; 6.165).[4] 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. A set of conclusions is potentially undone once any of its fundamental postulates is disproved. In this case, the observation of a single black swan would be the undoing of the phrase's underlying logic, as well as any reasoning that followed from that underlying logic.

Juvenal's phrase was a common expression in 16th century London as a statement of impossibility. The London expression derives from the Old World presumption that all swans must be white because all historical records of swans reported that they had white feathers.[5] In that context, a black swan was impossible or at least nonexistent. After Dutch explorer Willem de Vlamingh discovered black swans in Western Australia in 1697,[6] the term metamorphosed to connote that a perceived impossibility might later be disproven. Taleb notes that in the 19th century John Stuart Millused the black swan logical fallacy as a new term to identify falsification.[7]

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