buckram vs buckrams

buckram

noun
  • A coarse cloth of cotton, linen or hemp, stiffened with size or glue, used in bookbinding to cover and protect the books, in garments to keep them in the form intended, and for wrappers to cover merchandise. 

  • A plant, Allium ursinum, also called ramson, wild garlic, or bear garlic. 

verb
  • To stiffen with or as if with buckram. 

buckrams

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