indoors vs internal

indoors

noun
  • The interior of a building; the space inside buildings generally. 

adv
  • Inside, into, or within a building. 

internal

adj
  • Within the body. 

  • Concerned with the domestic affairs of a nation, state or other political community. 

  • Of the inner nature of a thing. 

  • Applied or intended for application through the stomach by being swallowed. 

  • Concerned with the non-public affairs of a company or other organisation. 

  • Attending a university as well as taking its examinations. 

  • Of or situated on the inside. 

  • Experienced in one's mind; inner rather than expressed. 

  • Present or arising within an organism or one of its parts. 

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