Brush Xs and Os - 2 Piece SetAncient Romans considered an X to be a sacred symbol, meaning faith and fidelity. During the middle ages, documents were sealed with an X embossed with wax. Then it was customary to kiss it afterward. Thats where the phrase sealed with a kiss comes from. And thats why the letter X represents a kiss to this day. O was later added to symbolize a hug. No one knows where or when. Scholars even hypothesized the game tic tac toe brought them together and it