unascertained vs up in the air

unascertained

adj

  • Not ascertained; undetermined; unknown. 

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 unascertained and up in the air occurred in a corpus of books? (source: Google Ngram Viewer )