breathing space vs dog sleep

breathing space

noun
  • A rest, pause, or respite. 

  • Enough distance so that one can feel unfettered. 

  • Sufficient space or a span of time in which to recover one's breath. 

dog sleep

noun
  • A shallow sleep; a pretended sleep. 

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