flattery vs testimonial

flattery

noun
  • An instance of excessive praise. 

  • Excessive praise or approval, which is often insincere and sometimes contrived to win favour. 

testimonial

noun
  • A tribute given in appreciation of someone's service etc. 

  • A statement, especially one given under oath; testimony 

  • A match played in tribute to a particular player (who sometimes receives a proportion of the gate money). 

  • A written recommendation of someone's worth or character 

adj
  • Serving as testimony. 

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