Douglas Harper's Etymology Dictionary
mirabile dictu
1831, Latin, literally "wonderful to relate." Found in Virgil.
Wiktionary
mirabile dictu
interj. wonderfully, amazingly; remarkable to say; It's a miracle!
Usage examples of "mirabile dictu".
But, mirabile dictu, the soupy string music continued, even though the Fox fell silent.
They did not own the school itself, mirabile dictu, but their offspring boarded a pair of Morgans there.