What is the origin of the idiom "at the crack of dawn" and when to use it?

The idiom "at the crack of dawn" refers to a very early time in the morning, typically at daybreak or just before sunrise. The phrase is used to describe activities or events that occur at the earliest part of the day. Its origin is uncertain, but it is believed to have originated in the late 1800s. The word "crack" in this context refers to the first light of the morning before the sun peeks over the horizon, symbolizing the beginning of the day,