leavings vs scobs

leavings

noun
  • A worthless and incidental residuum, such as scraps from a meal, or shavings or sawdust from wood. 

scobs

noun
  • raspings of wood, ivory, hartshorn, metals, or other hard substance 

  • The dross of metals. 

How often have the words leavings and scobs occurred in a corpus of books? (source: Google Ngram Viewer )