flatland vs heathland

flatland

noun
  • Synonym of plain: land of relatively constant altitude, usually exclusive of forests, deserts, and wastelands. 

  • An urban region with many flats or apartments to rent. 

heathland

noun
  • A tract of scrubland habitats characterised by open, low growing woody vegetation, found on mainly infertile acidic soils. Similar to moorland but with warmer and drier climate. 

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