
Why must we keep elbows off the table?
One theory: During the Middle Ages, the tables in the great houses were made from trestles, and diners sat along one side only. If they leaned on the table with their elbows, the whole thing could collapse.
When you eat soup, why is it proper to spoon away, not toward yourself?
To keep spills from your lap. But this is only in the Western world; in parts of the East, it's courteous to spoon inward since it's more noble to spill on yourself than on the table, which interrupts others' mealtime.
Why should we sit up straight at the table?
It isn't just a sign of decorum. When you slouch, you compress your stomach and intestines, which may make digestion difficult.
Why do we say "God bless you" after a sneeze?
Two of many answers: Pope Gregory the Great, who lived through the Justinian plague, blessed any sneezer, in hope that he or she wouldn't develop the plague. Also, some believed the heart stops when you sneeze; the blessing is a plea for life to return, or congratulations at the heart's restart.