On this day in 600 A.D., Pope Gregory the Great is said to have coined the phrase “God bless you” for when somebody sneezed.
The Justinian Plague, which began in 541 A.D., is so called because it took place while Justinian I (c. 482-565) was emperor of the Byzantine Empire. It is said to have killed up to 5,000 people a day, or 25 million people worldwide. An early symptom of the plague was sneezing. By saying “God bless you,” people hoped that the disease could be halted in the one who had sneezed.