empty space vs open space

empty space

noun
  • An unoccupied area or volume. 

  • Vacuum; a space containing nothing at all 

  • An unoccupied space where something may be stored 

  • A feeling of longing for someone or something that is gone; a sense of a thing's absence. 

open space

noun
  • An open-air area, such as a park or public garden with no (or very few) buildings, often in an urban area and designated by a local authority or government as such. 

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