ingratiate vs slip in

ingratiate

verb
  • To bring oneself into favour with someone by flattering or trying to please him or her. 

  • To recommend; to render easy or agreeable. 

slip in

verb
  • To include (e.g. a certain word or phrase) into a sentence discreetly 

  • To enter discreetly 

  • To play a subtle pass into someone in a goalscoring position. 

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