old soul

What is an old soul?
I can't remember what came first in my life, feeling like i had thousands of years worth of wisdom to call upon, or someone putting that idea into my head by calling me an old soul. I do know that i've liked it when people have perceived me in such a way. I hope that's not just vanity, and that in some way i've been a little worthy.
I remember when i was a very young adult, and my father's mate Bonnie, one of the gentlest people i've ever known, compared me to my father. She said that i was spiritually much older than he, and that i'd been born old (which may be an unfortunate description if perceived from the wrong direction, so let me quickly point out that old souls are often the most childlike people around).
What is an old soul? Just a poetic way of saying "wise"?
I remember once being told that flecks in the iris are the mark of a human who has lived many lifetimes, and is near the end of their time on earth. Even though this seems the fancifullest of foofery (and i'm in no rush to end my journey on Earth), the thought sparked my romantic notions...particularly as the person telling me was remarking on the abundance of flecks in my eyes.
Is "old soul" simply a reflection of intelligence? The wielding of a nine-pound brain in an eight-pound world? Being able to grasp the larger perspectives that elude most?
Is it the literal, an affirmation of the immortality of the soul, or human reincarnation? I can't speak to that, i'm merely wise enough to know that any such ponderings are rife with pitfalls of illusion and self-deception.
I can only relate to you my knowledge of old souls by description, not definition. When i meet someone who strikes me as an old soul, it's spiritual peacefulness i spy. Old souls know what's important. If they live lives that perplex the average person, it's because they understand more. Old souls know what's worth getting upset about (or rather more to the point, what's not). Old souls know that if everyone could rise above themselves to more clearly perceive the universe and their own life, they would realize that most of us spend a lifetime worrying about things we have no control over, things that will be gone tomorrow, and simple trivialities.
Perhaps old-soulness is about the elimination of worry altogether. Lost your job? Lost your way? A rogue asteroid is nigh? Even then the old soul may be simply cherishing a moment of life, while others gnash.
My own favorite description of an old soul may be less accurate than the preceding one, but i like to think of old souls in terms of fear. That the measure of the age of any soul, is in direct proportion to how much that person overcomes the fears we all carry from cradle to grave. Perhaps i just like that description, because along with feminism and psychosexual repression, fear is the windmill i tilt at most passionately.
But not obsessively. Life's too short.