in doubt vs pending

in doubt

adj
  • uncertain, unclear, unsure 

pending

adj
  • About to happen; imminent or impending. 

  • Begun but not completed. 

  • Awaiting a conclusion or a confirmation. 

prep
  • While waiting for something; until. 

  • During. 

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