bivvy vs camp out

bivvy

verb
  • To erect, or to stay in, such a tent or shelter. 

noun
  • A small tent or shelter. 

camp out

verb
  • To sleep outdoors, often in a tent. 

  • To wait or queue for something expected to occur, often overnight. 

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