Why do Chinese people like to use egg to describe a person? For example, 坏蛋, 糊涂蛋, 穷光蛋, 王八蛋.

I'm glad to talk about it with you. 坏蛋 refers to be bad eggs originally. later, it extends to people. 王八蛋 is said that comes from "忘八端". because they have similar pronunciation, so it changes 王八蛋. 八端 is eight standards of behavior. 八端 refers to "孝，悌，忠，信，礼，义，廉，耻" in ancient times. it's root of being a human. forgetting "八端" is just forget the basic root of being a human. it's a swear word whether now or not. 穷光蛋 is very poor. especially in ancient times, they have a larger gap between the poor and the rich, someone maybe have nothing, even an egg. I think it's a metaphor. I guess the rest maybe extend from others.