bivvy vs bivy

bivvy

verb

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

noun

  • A small tent or shelter. 

bivy

verb

  • To camp in a bivouac. 

noun

  • A bivouac sack. 

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