keep down vs rule despotically

keep down

verb
  • To cause not to increase or rise. 

  • To repress. 

  • Not to vomit. 

  • To restrain or control (a sound). 

  • To lie low. To stay concealed by not standing up 

rule despotically

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