backpedal vs walk back

backpedal

verb
  • To distance oneself from an earlier claim or statement; back off from an idea. 

  • To pedal backwards on a bicycle. 

  • To step backwards. 

walk back

verb
  • To withdraw or backpedal on a statement or promise. 

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

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