tergiversator vs viper

tergiversator

noun
  • one who tergiversates 

viper

noun
  • A dangerous, treacherous, or malignant person. 

  • A person who smokes marijuana. 

  • A venomous snake in the family Viperidae. 

  • Any venomous snake. 

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