grail vs mandible

grail

noun
  • One of the small feathers of a hawk. 

  • Small particles of earth; gravel. 

  • Something eagerly sought or quested for. 

  • The Holy Grail. 

  • A book of offices in the Roman Catholic Church; a gradual. 

mandible

noun
  • Either of the upper and lower segments of a bird's beak. 

  • Any of various invertebrate mouthparts serving to hold or bite food materials. 

  • One of the anterior pair of mouthparts of an arthropod, designed for holding and cutting food. 

  • The jaw or a jawbone, especially the lower jawbone in mammals and fishes. 

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