grout vs gypsum

grout

noun
  • A thin mortar used to fill the gaps between tiles and cavities in masonry. 

verb
  • To insert mortar between tiles. 

  • To affix with mortar. 

gypsum

noun
  • A mineral consisting of hydrated calcium sulphate. When calcinated, it forms plaster of Paris. 

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