curious vs unsolvable

curious

adj
  • Containing or pertaining to trivalent curium. 

  • Tending to ask questions, or to want to explore or investigate; inquisitive; (with a negative connotation) nosy, prying. 

  • Leading one to ask questions about; somewhat odd, out of the ordinary, or unusual. 

  • Caused by curiosity. 

unsolvable

noun
  • A problem that cannot be solved. 

adj
  • Not solvable. 

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