castoff vs unfit

castoff

adj
  • discarded, rejected. 

noun
  • Something that has been rejected or discarded; a reject. 

unfit

adj
  • Unsuitable for a particular purpose. 

  • Not fit; not having the correct requirements. 

  • Not fit, not having a good physical demeanor. 

verb
  • To make unfit; to render unsuitable, spoil, disqualify. 

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