What is the origin of the idiom "first light" and when to use it?

The origin of the idiom "first light" can be traced back to the natural phenomenon of the sun rising and illuminating the sky. The term "first light" has been used for centuries to describe the initial appearance of daylight at the beginning of each day. As humans have long been attuned to the cycles of day and night, the concept of "first light" likely emerged as a way to describe the earliest moments of dawn, when the sky transitions from darkness to light. Over time, the phrase became a part of everyday language and is now commonly used to refer to the early stages of daylight.