hesitation vs uncertainty

hesitation

noun
  • doubt; vacillation. 

  • A faltering in speech; stammering. 

  • An act of hesitating 

uncertainty

noun
  • Something uncertain or ambiguous. 

  • Doubt; the condition of being uncertain or without conviction. 

  • A parameter that measures the dispersion of a range of measured values. 

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