Why does the letter 'x' stand for a kiss?

The use of 'x' to represent a kiss dates back to the Middle Ages when people would sign documents with an 'X' as a symbol of their faith, often kissing it to show sincerity. The 'X' was seen as a representation of a person, and the act of kissing it added a personal touch. Over time, this practice evolved into the modern convention of using 'x' at the end of letters and messages to signify affection and love.