bethink vs look back

bethink

verb
  • To think of (something or somebody) or that (followed by clause); to remind oneself, to consider, to reflect upon. 

  • To meditate, ponder; to consider. 

  • To determine, resolve. 

look back

verb
  • To reconsider or regret. 

  • To think of (past events) in retrospect. 

  • Used other than figuratively or idiomatically: see look, back. 

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