internment vs slavery

internment

noun
  • Confinement within narrow limits, as of foreign troops, to the interior of a country. 

slavery

noun
  • A condition of servitude endured by a slave. 

  • A condition in which one is captivated or subjugated, as by greed or drugs. 

  • An institution or social practice of owning human beings as property, especially for use as forced laborers. 

  • Forced labor in general, regardless of legality. 

adj
  • Covered in slaver; slobbery. 

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