adobe vs flagstone

adobe

noun
  • An unburnt brick dried in the sun. 

  • The earth from which such bricks are made. 

  • A house made of adobe brick. 

flagstone

noun
  • A flat, rectangular piece of rock or stone used for paving or roofing. 

  • One of several types of rock easily split and suitable for making flagstones. 

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