unsure vs up in the air

unsure

adj

  • uncertain 

  • unstable or precarious 

up in the air

adj

  • Not yet resolved, finished, answered, decided or certain. 

adv

  • Used other than figuratively or idiomatically: see up, in, the, air. 

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