cast off vs wash one's hands of

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. 

wash one's hands of

verb
  • To absolve oneself of responsibility or future blame for; to refuse to have any further involvement with. 

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