mnemonic vs testimonial

mnemonic

noun
  • Something (especially a series of ideas, letters, words, etc.) used to help in remembering a thing; a memory aid. 

  • The human-readable, textual form of an assembly language instruction, not including operands. 

adj
  • Of or relating to memory. 

  • Especially of a series of ideas, letters, words, etc.: intended to help in remembering. 

  • Of or relating to mnemonics (“the study of techniques for remembering anything more easily”). 

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 mnemonic and testimonial occurred in a corpus of books? (source: Google Ngram Viewer )