certifiably vs to be sure

certifiably

adv
  • Undoubtedly, demonstrably. 

  • With the potential for certification. 

  • To a great extent. 

  • Genuinely 

to be sure

adv
  • Certainly, undoubtedly, admittedly. 

How often have the words certifiably and to be sure occurred in a corpus of books? (source: Google Ngram Viewer )