cast off vs turn one's back on

cast off

verb
  • To discard or reject something. 

  • To let go (a cable or rope securing a vessel to a buoy, wharf, etc.) so that the vessel may make way. 

  • To finish the last row of knitted stitches and remove them securely from the needle. 

  • To estimate the amount of space required by the type used for the given copy. 

turn one's back on

How often have the words cast off and turn one's back on occurred in a corpus of books? (source: Google Ngram Viewer )