[tomjakubowski]

An unexpected event being "good" doesn't make it a "white swan". The historical context for black swans is that Europeans had only ever seen white swans, which were native to the Old World, and so there was assumption among them that all swans were white: the black swan in European culture was a symbol for something impossible. That is, until they made contact with Australia, and first encountered the black swan. One who had derived from induction the mistaken assumption that all swans were white was proven wrong with a single observation, and the European models and cultural symbols had to be updated.

https://theconversation.com/friday-essay-a-rare-bird-how-eur...

An observation consistent with past observations would be a "white swan".