intelligibility vs thoughtlessness

intelligibility

noun
  • The quality of recorded speech of every word being understandable. 

  • That which is intelligible; the degree to which something is intelligible. 

thoughtlessness

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

  • disregard for other's feelings 

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