What is the origin of the idiom "on top of the world" and when to use it?

The origin of the phrase "on top of the world" can be traced back to the concept of physical elevation and the association of being at the highest point. Over time, the phrase has evolved to be used in various contexts to describe moments of personal achievement, happiness, or contentment. It is often employed when individuals experience a significant success or accomplishment in their professional, academic, or personal lives.