uncertainty vs unconfidence

uncertainty

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

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

  • Something uncertain or ambiguous. 

unconfidence

noun
  • Absence of confidence; uncertainty; doubt. 

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