backpedal vs send 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. 

send back

verb
  • To remind (someone) of a previous time in the past. 

  • To return (something) to its origin. 

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