"Ride a dog and your crotch will rot" is a common saying, which means riding a dog will cause your crotch to rot. The origin of this saying may have the following explanations:

Hygienic issues: Dogs may have parasites, bacteria or other Contaminants, close contact with dogs may bring health risks, leading to skin infection, ulceration and inflammation, so there is a saying that "riding a dog will ruin your crotch".

Safety issues: Adults are worried that children will be thrown off when riding a dog, or the dog will get angry and bite them, so they use "dog riding to ruin their crotches" to scare children.

Cherish items: In the past, people's living conditions were difficult, and a piece of clothing might be worn all year round. Children also cherish their clothes very much, for fear of being worn out or hung up. In order to get children to take good care of their clothes, adults use "rotten crotch" to scare children.