gypsum vs quicklime

gypsum

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

quicklime

noun
  • Calcium oxide, which is produced by heating (calcining) limestone and gives slaked lime on treatment with water. 

verb
  • To treat with quicklime. 

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