service area vs threshing floor

service area

noun
  • A place built alongside a limited-access road where one can stop to buy fuel, refreshments, and so on. 

threshing floor

noun
  • The floor of a threshing house or similar area where grain is threshed. 

How often have the words service area and threshing floor occurred in a corpus of books? (source: Google Ngram Viewer )