The common custom of placing an X on envelopes, notes, and at the bottom of letters to mean kisses dates back to the Middle Ages, when a Christian cross was drawn on documents or letters to represent sincerity, faith, and honesty. In fact, the person who signed the document often kissed the cross as a display of a sworn oath that this was his “mark.” In Christian history, the X was part of the symbol representing Christ, giving rise to the practice of using the letter X and a kiss to symbolize a sacred oath. There is much speculation regarding the meaning of the O. Some sources cited instances in which the O represented two half circles uniting, making a completed circle symbolizing a hug. Another perspective from North American descent is that Jewish immigrants who came to the United States used an O to sign documents in place of an X, rather than making a sign that might represent the cross of Jesus. Of course, any teacher who has collected “love notes” knows that X’s and O’s just means that one student has a whopper of a crush on someone!