Rub Off Meaning

(idiomatic) to be transferred with little or no effort

Example: To cause to come off by rubbing
  We had to rub off all the graffiti from the wall
To clean by rubbing.
1922, Margery Williams, The Velveteen Rabbit
  He was wet through with the dew and quite earthy from diving into the burrows the Boy had made for him in the flower bed, and Nana grumbled as she rubbed him off with a corner of her apron.