mortar vs plaster of Paris

mortar

noun
  • A mixture of lime or cement, sand and water used for bonding building blocks. 

  • A muzzle-loading, indirect fire weapon with a tube length of 10 to 20 calibers and designed to lob shells at very steep trajectories. 

  • A hollow vessel used to pound, crush, rub, grind or mix ingredients with a pestle. 

  • In paper milling, a trough in which material is hammered. 

verb
  • To attack (someone or something) using a mortar (weapon). 

  • To pound in a mortar. 

  • To use mortar or plaster to join two things together. 

  • To fire a mortar (weapon). 

plaster of Paris

noun
  • A hemihydrate of calcium sulfate, made by calcining gypsum, that hardens when moistened and allowed to dry; used to make casts, molds and sculpture. 

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