buttons vs tomentum

buttons

noun
  • A small South African plant of the genus Conophytum, with button-like succulent leaves covering its exterior. 

  • Synonym of marbles (“sanity; mental faculties”) 

  • The dung of sheep. 

  • A remote control. 

  • A policeman. 

tomentum

noun
  • A mass of filamentous hairs on the leaf of a plant. 

  • A network of fine blood vessels between the pia mater and the cerebral cortex. 

  • A covering of fine, soft hairs; a pubescence. 

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