consonance vs synchronism

consonance

noun
  • Harmony; agreement; lack of discordance. 

  • The repetition of consonant sounds, but not vowels as in assonance. 

synchronism

noun
  • The state of being synchronous. 

  • The tabular arrangement of contemporary events etc. in history. 

  • A temporal relationship between events. 

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