A preposition.

Glikeria   Wed Jul 19, 2006 10:36 am GMT
Here is a limerick.
There was an old maiden from Fife
Who had never been kissed in her life
Along came a cat,
So she said, “I’ll kiss that!”
But the cat answered, “Not on your life!”

ON in the cat’s answer seems strange to me. How common is this expression?