somnolence vs syncopation

somnolence

noun
  • A state of drowsiness or sleepiness. 

syncopation

noun
  • The contraction of a word by means of loss or omission of sounds or syllables in the middle thereof. 

  • The quality of a rhythm being somehow unexpected, in that it deviates from the strict succession of regularly spaced strong and weak beats in a meter. 

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