羊? + 大 = 美
How to understand the origin of 美：
A big fat sheep is certainly nice to eat.
It’s a beautiful thing to eat the sheep meat.
Sheap is the main animal to provide meat for people among the 六畜 six domestic animals. The six domestic animals in ancient times were horses, cattle, sheep, chickens, dogs and pigs.
So, the ancient people considered sheep beautiful and then created 美.
That’s why there are expressions such as 美食，美味，美餐，etc.
The original meaning of 美 is similar to that of 善 and 義.