terrane vs topsoil

terrane

noun
  • A block of the Earth's crust that differs from the surrounding material, and is separated from it by faults. 

topsoil

noun
  • The most fertile soil, easiest to start new plants in. 

verb
  • To remove the topsoil from. 

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