guess vs surmise

guess

verb
  • to suppose (introducing a proposition of uncertain plausibility). 

  • To solve by a correct conjecture; to conjecture rightly. 

  • To reach a partly (or totally) unqualified conclusion. 

  • To think, conclude, or decide (without a connotation of uncertainty). Usually in first person: "I guess". 

noun
  • A prediction about the outcome of something, typically made without factual evidence or support. 

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 guess and surmise occurred in a corpus of books? (source: Google Ngram Viewer )