It's the guy to blame when the Fed's come knocking on your door.
A body double
A vision of one's self out of the corner of your eye.
I heard her say, "Now that's one good looking doppelgänger."
In folklore it's a harbinger of back luck:
a) When you see your own doppelgänger, it's an omen of death.
b) When you see a relative's or friend's doppelgänger it could mean illness or bad luck for him/her.
German origin: 2 words a)Doppel- double b)Gänger- walk or walker