impending vs in the air

impending

adj
  • Approaching; drawing near; about to happen or expected to happen. 

noun
  • Something that impends or threatens; an expected event. 

in the air

prep
  • Unsupported and liable to be turned or taken in flank. 

  • In the surrounding ambience. 

  • Not in a fixed or stable position; unsettled; up in the air. 

  • Prevalent without traceable origin or authority. 

  • In the generally prevailing feeling, idea, atmosphere, or mood. 

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