motivate vs surmise

motivate

verb
  • To animate; to propel; to cause to take action 

  • To provide someone with an incentive to do something; to encourage. 

surmise

verb
  • To imagine or suspect; to conjecture; to posit with contestable premises. 

noun
  • Thought, imagination, or conjecture, which may be based upon feeble or scanty evidence; suspicion; guess. 

  • Reflection; thought; posit. 

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