ovoid vs yolk

ovoid

noun
  • Something that is oval in shape. 

adj
  • Egg-shaped; shaped like an oval, but more tapered at one end; ovate. 

  • Shaped like an oval. 

yolk

noun
  • The yellow, spherical part of an egg that is surrounded by the white albumen, and serves as nutriment for the growing young. 

  • The grease in a sheep's fleece; lanolin. 

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