forgetfulness vs thoughtlessness

forgetfulness

noun
  • Failure to bear in mind; careless omission; inattention. 

  • Loss of remembrance or recollection; a ceasing to remember; oblivion. 

  • The quality of being forgetful; proneness to let slip from the mind. 

thoughtlessness

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

  • disregard for other's feelings 

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