corroboration vs testimonial

corroboration

noun
  • That which corroborates. 

  • The act of corroborating, strengthening, or confirming; addition of strength; confirmation 

testimonial

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

  • A written recommendation of someone's worth or character 

adj
  • Serving as testimony. 

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