Why is "Dragon Bell" used to refer to the appearance of the elderly? Any allusions?

Li Duan, a poet in the Tang Dynasty, wrote a poem "To Xuedai": "When you make friends, you are ashamed of your generation, and the dragon bell is like an old man." Wang Zhidao's Ci in Song Dynasty: "Idle away my years, my hair is floating with the wind, and people are getting old. My heart is still strong, I can see the degree of words and walk alone in Jiangdong. " [Man and Yuan Fadi drink in autumn] Lu You's poem "Listening to the Rain" says: "It is better to be old and dying than to be defeated by the secular." It shows that the term "Dragon Bell" has been popular in the Tang and Song Dynasties. Someone in the Song Dynasty also expressed this feeling: "I've always wanted to cut jiaozi and catfish with a sword and halberd. Chen Hu didn't sweep, and ordered a strong man to pull the Tianhe River. Who would have thought that half a lifetime's troubles would lead to old age and gray hair more and more every year. There is no fear on the outside, and the heart is also afraid of wind and rain. " Getting old is a natural law. Fear, sighing and feeling old are also natural mentality. However, Bai Letian said in a poem, "Seven people are in their fifties and seventies, with purple flowers and white beards. Without gold in your hand, you are happy with wine in the bottle ... "Lu You said:" The small house is quiet and comfortable, and you can read and write with your partner; I don't mean to be old, I just like to be old in winter. " When people are old, they may get together with friends or spend time with their children and grandchildren. The spirit of the ancient people, which makes people feel sad and cheerful, is worthy of our future generations' admiration and imitation. It is gratifying that there are many people approaching old age and their living conditions have undergone earth-shaking changes. How many old people are not old in our city? At present, the word "Dragon Bell" should be interpreted in the opposite direction: energetic, sounding like Hong Zhong, not old in posture, not old in mentality, studying, working, happy and happy. This is the fitness posture of many old people in China. As the saying goes; The old horse crouches, and the old man is strong and strong, and he travels all over the green hills.