outlier vs rara avis

outlier

noun
  • A person or thing situated away from the main body or outside its proper place. 

  • A part of a formation separated from the rest of the formation by erosion. 

  • An exception. 

  • A value in a statistical sample which does not fit a pattern that describes most other data points; specifically, a value that lies 1.5 IQR beyond the upper or lower quartile. 

rara avis

noun
  • A rare or unique, and thus outstanding or unusual, person or thing; a rare bird. 

  • A rare species or type of bird. 

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