Definition & Meaning of "bright-eyed and bushy-tailed"

What is the origin of the idiom "bright-eyed and bushy-tailed" and when to use it?

The exact origin of the phrase "bright-eyed and bushy-tailed" is uncertain, but its earliest known usage dates back to the mid-20th century. It is believed to have originated in the United States, possibly inspired by the behavior and appearance of certain animals, such as squirrels or rabbits, which are known for their alertness and energetic nature. This idiom is often heard in casual conversations, workplace settings, or social interactions where people are discussing their state of mind or readiness for the day ahead. It is frequently used when someone appears refreshed, optimistic, and eager to tackle challenges or participate actively in activities.