gypsum vs parget

gypsum

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

parget

noun
  • Plaster, as for lining the interior of flues, or for stuccowork. 

  • Gypsum. 

verb
  • To coat with gypsum; to plaster, for example walls, or the interior of flues. 

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