Life is impermanent, and the large intestine encloses the small intestine. What kind of stalk is it?

The term "large intestine enveloping small intestine" means that life is impermanent, and many things are unpredictable. Everyone should be optimistic and positive, and don't care so much, which can better reflect the mentality of young people now. When this stalk is gradually known by more people, it is usually used in some funny videos, or in unlucky and embarrassing social death scenes.