Qianlong was the fourth son of Yongzheng. Why is he called "Huang San Ye with iron teeth and copper teeth" in Ji Xiaolan? Why is small Shenyang called "He Er"?

Actually, I have thought about this question, but Ji Xiaolan's films are mainly written around the enemies of the emperor, Ji Xiaolan and Shenyang. At the beginning, Ji Xiaolan urged the emperor to go to the south to rescue Geng Chen and her father. In order to fool Xiao Shenyang, he was called "He Er". He called himself Lao Ji, which means that he took a little advantage of Xiao Shenyang O(∩_∩)O~