from Wiktionary, Creative Commons Attribution/Share-Alike License
- A "happy fault" or "fortunate fall".
- A series of miserable events will eventually lead to a happier outcome.
- The Biblical story of the fall of Adam and Eve and the loss of the Garden of Eden, known theologically as the source of original sin - meaning that this loss of innocence was a fortunate fall because of the good that would come from it, that is, Christian redemption and the eventual hope of Heaven.
From Latin fēlīx culpa ("happy fault"), in Roman Catholic theology. (Wiktionary)