doubtfulness vs equivocation

doubtfulness

noun
  • The state or quality of being doubtful; doubt; uncertainty. 

equivocation

noun
  • The use of expressions susceptible of a double signification, possibly intentionally and with the aim of misleading. 

  • A logical fallacy resulting from the use of multiple meanings of a single expression. 

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