mistrust vs unbelief

mistrust

noun
  • Lack of trust or confidence; distrust, untrust. 

verb
  • To be suspicious. 

  • To have no confidence in (something or someone). 

  • To be wary, suspicious or doubtful of (something or someone). 

  • To suspect, to imagine or suppose (something) to be the case. 

unbelief

noun
  • An absence (or rejection) of belief, especially religious belief 

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