It say AD "was conceived around the year 525 by the Christian monk Dionysius Exiguus. He did this to replace the then dominant Era of Martyrs system, because he did not wish to continue the memory of a tyrant who persecuted Christians." So AD itself was a neologism to avoid mentioning something offensive (or someone offensive, Diocletian).
https://en.wikipedia.org/wiki/Common_Era#History
It say AD "was conceived around the year 525 by the Christian monk Dionysius Exiguus. He did this to replace the then dominant Era of Martyrs system, because he did not wish to continue the memory of a tyrant who persecuted Christians." So AD itself was a neologism to avoid mentioning something offensive (or someone offensive, Diocletian).