In the Spring and Autumn Period, Duke Jing of the state of Jin fell ill. One night, he dreamed that his disease had transformed into two small figures talking beside him. One said, "I'm afraid the doctor will harm us." The other replied, "Don't worry. We can hide above huang and below gao. Then the doctor will be able to do nothing to us."
The next day, after examining the duke, the doctor said, "Your disease is incurable, I am afraid, Your Majesty. It's above huang and below gao, where no medicine can reach."
This idiom indicates a hopeless or terminal condition.