Определение и Значение "swan song"

What is the origin of the idiom "swan song" and when to use it?

The idiom "swan song" originates from the ancient belief, dating back to Greco-Roman mythology, that swans sing a beautiful, haunting melody just before their death. This belief was perpetuated in various literary works, including the Roman poet Virgil's writings. Over time, this expression evolved to describe a final, notable performance or effort before retiring, leaving a position, or coming to the end of a career.