Soft on the outside and hard on the inside, what is it?

The phrase "soft on the outside and hard on the inside" became popular unconsciously. I thought it was an idiom, but I couldn't find the idiom "soft on the outside and rigid on the inside" in the idiom dictionary from morning till night, which is puzzling! "Soft outside and rigid inside", as the name implies, means soft outside and rigid inside. I close my eyes, and many things with soft appearance and hard heart emerge in my mind. Tumors, you must be familiar with them, right? What scares people is cancer cells. There are thousands of cancer cells in tumors in Qian Qian. This kind of cell is typical of soft outside and hard inside. The soft coat is wrapped in a diamond-like hard core. Because of this special structure, there is no good medicine to kill it so far. No matter how strong the body is, once it is invaded by this kind of thing, it is hopeless. These greedy cancer cells will devour normal cells in your body crazily. Their existence, their existence, from cancer cells, I think of eunuchs, eunuchs, commonly known as hermaphrodites. What should have come out was cut across the board, leaving soft flesh and tissue underneath. These are just its appearance, but the inside is just the opposite. Because the testicles are gone, there is a lack of androgens that men should have, and estrogen is multiplied in the body, making the lower body that has not cut off its roots always restless and hard as an iron bar. This kind of thing that is neither male nor female is typical of softness on the outside and rigidity on the inside. I heard that there are a lot of such inferior goods in Beijing. From the eunuch, I think of the masturbation device used by women, which is soft in appearance. I touched it with my hand and squeezed it hard, only to know that it was as hard as steel. It turns out that the inside is made of steel bars, and the combination of soft outside and hard inside forms a masturbation toy. This thing has no other function, which can make people fantasize and masturbate. Suddenly, I thought of something hard outside and soft inside, coconut: a good thing, with an indestructible appearance, but inside its hard appearance, it is wrapped in a layer of white sweet pulp, and the pulp is full of sweet liquid. I saw the United States from the coconut, and I saw many democratic countries with hard outside and soft inside.