bivvy vs encampment

bivvy

noun

  • A small tent or shelter. 

verb

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

encampment

noun

  • A campsite. 

  • A group of temporary living quarters and/or other temporary structures. 

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