castoff vs thoughtlessness

castoff

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

adj
  • discarded, rejected. 

thoughtlessness

noun
  • heedless disregard for the consequences of one's actions 

  • disregard for other's feelings 

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