This famous Latin pun is attributed to the future Pope Gregory the Great in the 6th century. According to the historian the Venerable Bede, Gregory was walking through a Roman slave market when he spotted strikingly fair-skinned, blond-haired boys.
He asked the slave trader where they were from, and was told they were Angles (an Anglo-Saxon tribe). Gregory made the wordplay “Non Angli, sed angeli”. When he learned they were pagans, he added “si Christiani”—stating they were beautiful enough to be angels, if only they were Christian.
This chance encounter heavily influenced history: it inspired Gregory (after he became Pope) to send St. Augustine of Canterbury to England in 597 AD to re-evangelize the Anglo-Saxons.
Image above: Glass inlay mosaic — Saints Augustine and Gregory, “Non Angli sed Angeli si Christiani…”
At Chapel of St Gregory and St Augustine, Westminster Cathedral — London.