teetering vs tentative

teetering

noun
  • A precarious motion or situation, risking a fall or collapse. 

tentative

noun
  • A trial; an experiment; an attempt. 

adj
  • restrained; polite; feeling one's way, not using full force. 

  • Uncertain; subject to future change. 

  • Of or pertaining to a trial or trials; essaying; experimental. 

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