Answer:
Although my cow is dead, I still beat herΒ What a racket she makes.
You heart it speak, for it has a hard tongue. But it cannot breathe, for it has not a lung.
I am free for the taking. Through all of your life, though given but once at birth. I am less than nothing in weight, but will fell the strongest of you if held.
What can be filled with empty hands?
I march before armies, a thousand salute me. My fall can bring victory, but no one would shoot me. The wind is my lover, one-legged am I. Name me and see me at home in the sky.
You use it between your head and your toes, the more it works the thinner it grows.