sawtooth vs serration

sawtooth

noun
  • A cutting bit of a saw. 

  • A sawtooth wave. 

  • Any of various pierid butterflies of the genus Prioneris. 

serration

noun
  • The state of being serrated. 

  • One of the teeth in a serrated or serrate edge. 

  • A set of teeth or notches. 

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