"Xi" is a folk word, which means that both men and women at the wedding are very happy. Generally, such folk words will not be included in ancient dictionaries, and their sources can only be legends.
As for the origin of the word "Xi", it is said that it was created by Wang Anshi. Wang Anshi, because he was cleverly betrothed to United Horse, on the wedding day, just as the bride and groom were worshipping heaven and earth, a newspaper reported: "Mr. Wang wants to be the top scholar, so please go to the Qionglin banquet tomorrow!" Father Ma was overjoyed and immediately reopened the banquet. In the face of double happiness, Wang Anshi wrote a big word "Xi" on red paper, which made people stick it on the door and recite casually: "The couplet is a double happiness song, and the lantern is flying." Since then, the word "Xi" has spread, and since then, the word "Xi" and the double happiness in marriage have become popular among China people.
There are many folk-custom characters in China, such as "longevity", "the way to make money", "two thousand gold" and "harmony between man and nature".