cast off vs rid

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. 

rid

verb
  • To free (something) from a hindrance or annoyance. 

adj
  • Released from an obligation, problem, etc. (usually followed by of). 

How often have the words cast off and rid occurred in a corpus of books? (source: Google Ngram Viewer )