In the past, the order of heaven, earth, mystery and yellow was sorted by thousands of words, and heaven was the first of thousands of words, so 1 means № 1. That is, A 1 in the current ranking. For example, in the imperial examination room, the first row is Tian Zi, the first one in the first row is Tian Zi No.1, and the first pronunciation of Tian Zi No.1 is Ti ā n zidi Yao, and Tian Zi's explanation is the first word of the first sentence of "thousand words". Refers to the first number in the first category. Metaphor is the highest, largest or strongest. The source is Ming Lingmengchu's "Surprise at the First Moment" Volume 18: "The harem beauty, inquiring is the guest's favorite concubine. Every day, she hired a Taihu boat with Tianzi No.1, set wine, played the piano and sang songs, and took this concubine down to the lake. " Tian is the first of ten thousand words. When the National Government inspected cultural relics in the Forbidden City, the first cultural relic it saw in the First Palace was listed as "Tian Zi No.1". However, this cultural relic is a wooden stool and is described as a joke.