mother-of-pearl vs nacre

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. 

nacre

noun
  • A pearly substance which lines the interior of many shells; mother-of-pearl. 

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