mother-of-pearl vs seashell

mother-of-pearl

noun
  • The hard pearly inner layer of certain mollusk shells; nacre. 

  • A butterfly of the genus Salamis. 

adj
  • Made from or looking like mother-of-pearl; iridescent or pearly. 

seashell

noun
  • The empty shell of a marine mollusk. 

  • A very light pink colour, like that of some seashells. 

adj
  • Of a very light pink colour, like that of some seashell. 

How often have the words mother-of-pearl and seashell occurred in a corpus of books? (source: Google Ngram Viewer )