hit it off vs prove out

hit it off

verb
  • To develop an amicable relationship (with), especially in a sudden manner during an initial encounter. 

prove out

verb
  • To turn out to be feasible, accurate, true, satisfactory, as expected, hoped, stated, etc. 

  • To demonstrate the feasibility of; to show or be shown to be feasible, accurate, true, satisfactory, as expected, hoped, stated, etc. 

How often have the words hit it off and prove out occurred in a corpus of books? (source: Google Ngram Viewer )