flocculus vs tussock

flocculus

noun
  • A small fluffy tuft. 

  • A marking on the surface of the sun associated with a solar prominence. 

  • Either of two small lobes on the posterior border of the cerebellum. 

tussock

noun
  • A tuft or clump of green grass or similar verdure, forming a small hillock. 

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