in use vs unoccupied

in use

prep

  • Currently being used. 

unoccupied

adj

  • Not occupied by foreign troops etc 

  • Not being used; vacant or free 

  • Not inhabited, especially by a tenant 

  • Not employed on a task; idle 

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