hot air vs intelligibility

hot air

noun
  • Air that has been heated, especially so as to function as the lifting agent of a hot-air balloon. 

  • Empty, confused, or exaggerated talk lacking meaning or substance; bluster. 

intelligibility

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

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

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