In ancient China, sexual intercourse was often viewed through the lens of Taoist practices, with the aim of enriching the spirit and cultivating life force. Common expressions included terms related to Yin and Yang, such as Yin Fu (vulva) and Yang Ju (penis), as well as practices detailed in texts on "Fangzhongshu," which focused on sexual skills and techniques. The term "zuo ai" (做爱) appears to be a more modern expression for "making love" or sexual intercourse. It's difficult to pinpoint the exact origin of "zuo ai," but its usage is more prevalent in contemporary Chinese.