keep on vs reoccupy

keep on

verb
  • To persist or continue. 

  • To cause or allow to remain in the on or open position. 

  • To cause or allow to remain in an existing position. 

  • To persist in talking about a subject to the annoyance of the listener. 

reoccupy

verb
  • To occupy again. 

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