centrifugal vs unusual

centrifugal

adj
  • Tending, or causing, to recede from the center. 

  • Expanding first at the summit, and later at the base, as a flower cluster. 

  • Having the radicle turned toward the sides of the fruit, as some embryos. 

noun
  • A rotating machine used to separate massecuite into sugar crystals and molasses. 

unusual

adj
  • Not usual, out of the ordinary. 

noun
  • Something that is unusual; an anomaly. 

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