indoors vs out-of-doors

indoors

noun

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

adv

  • Inside, into, or within a building. 

out-of-doors

adv

  • outdoors; outside. 

noun

  • outdoors 

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