at it vs occupied

at it

prep
  • Engaged in sexual intercourse or other sexual activity. 

  • Occupied with a given activity; busy with something. 

occupied

intj
  • Used to communicate that a toilet is unavailable. 

adj
  • Busy, unavailable. 

  • Reserved, engaged. 

  • Subjugated, under the control of a foreign military presence. 

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