When do we use these words? more often when a person sneezes. But why do we say "bless you"? Let's explore the reason. In the year 1665-66 in England, there happened a great plague. It was a Bubonic plague which is usually transmitted through the bite of an infected rat. This plague was so barbaric that it took almost 10,000 lives i.e. about 15% of the population of England. The final - fatal symptom of the Black Death was Sneezing and Coughing. So when a person sneezed, people surrounding him, blessed him by saying - "Bless you" (so that you are not suffering from the Great Black Death). This word was used so frequently that it became a fashion and the next generation started following the same without being aware of the actual reason. The description of the Great Black Death is even described in a nursery rhyme which we sang while playing. can u guess the rhyme? I will give you a hint - " it has a line - we all fall down" Yes. It is -"