Tian Yan means that the male sexual organs are underdeveloped and infertile. Tian Yan, also known as Tian Huan and Yin Gong, means a man with a short or even missing penis. Or a hermaphrodite who is not male or female.
According to Tao Zongyi's Record of Dropping out of Farming in Nancun (Volume 28) in Yuan Dynasty: "Yellow Gate: There are men who marry women and have no children for life, which are called castration in heaven, while the secular life is called yellow gate. "
Extended information:
Pan Zuyin (183 ~ 189) was an official, calligrapher and bibliophile in the Qing Dynasty, with a prominent family background. His grandfather was Pan Shien, the top scholar of the Qianlong Academy of Decadence and Ugliness, and his official was a master of Taifu and Wuyingdian. His father was Pan Zengshou. His great-uncle is Pan Shihuang, a flower explorer in Ganlong family.
However, he was born with hypoplasia. According to Lingxiao Xu Xu Yishi's Essays on a Master of Lingxiao, "Pan Zuyin is a neat freak and doesn't sleep with his wife." Quoting Jin Gyeong Zhong's Guili Li Qing Tan, he said, "(Pan Zuyin) was a heavenly eunuch in the Shang Dynasty, just like Weng Changshu. A student didn't know it. At the beginning of his visit, he asked the teacher several brothers. The minister said, don't you know that I am castrated? "
Reference: Baidu Encyclopedia _ Tian Yan.