The symbol is the Chinese character for "double happiness," (song hỉ in Vietnamese) and (shuangxi in Chinese). Wang Anshi (1021-1086), a famous Chinese politician during the Song Dynasty, created the symbol. When he was twenty, Wang Anshi traveled to the capital to sit the royal exams. During his journey, as he passed through a small town, he saw a sentence written on a paper banner that hung from a lantern near a house gate. A decorative revolving screen inside the lantern cast shadows on the lamp shade. The banner read, "The lantern of the pulling horses: The horses gallop when the lamp burns but halt when the lamp is snuffed.".
Wang realised that the house owner, a landlord named Mã (Horse), was inviting passers-by to create a pair of perfect parallel sentences by writing a second sentence to match. Smiling, Wang said to himself, "It's so simple!".
One of Mr. Mã's servants overheard Wang's remark and rushed to tell his master. Mr. Mã ordered the servant to invite Wang in, but by the time the servant returned to the gate, Wang had moved on.
Wang passed his qualifying exams. During the final test, the chief examiner showed him a flag embroidered with a tiger and read aloud this first line of a pair of possible parallel sentences: "The flag of the flying tiger: The tiger soars when the flag flies but rests when the flag is furled." Wang promptly recited the sentence he had seen at Mr. Mã's house. The two sentences matched perfectly, impressing everyone.
On his way back to his home village, Wang passed Mr. Ma's house. The servant recognised Wang and invited him in. When Mr. Ma implored Wang to give him a parallel sentence for the one posted on his gate, Wang recited the sentence from the exam. Of course, once again, the two sentences matched perfectly. Mr. Ma was so pleased that he offered Wang his daughter in marriage. In fact, it turned out that Mr. Ma's daughter had written the sentence on the gate to attract a talented husband.
On his wedding day, Wang learned that he had passed the royal exam with high distinction. Now, he could celebrate two events. He was so overjoyed that he wrote the character "double happiness" on a piece of red paper and pasted it on the gate. He then recited the following verse:
My ability to make parallel sentences has brought me double happiness.
The flying tiger and the running horses join in this auspicious marriage.