bash / zsh脚本中“case”语句的奇怪语法是什么原因？

Looking from a programmer's point of view then shell script is just another programming language, where one has to learn and conform to the rules of the language. However, I have to admit that this syntax is the weirdest style I have ever seen in a rather commonly used language. Did the shell take this syntax from an older language that it descents from? Is there a special implication / meaning in the syntax?Looking from a programmer's point of view then