Dust

"Dear Lord," the preacher began with arms extended and a rapturous 
look on his upturned face, "without you we are but dust..." 

He would have continued, but at that moment one very obedient little 
girl (who was listening carefully) leaned over to her mother and 
asked quite audibly in her little girl voice, "Mommy, WHAT is butt 
dust?" 
    -- http://www.netfunny.com/rhf/jokes/05/Nov/dust.html