Whitman's sampler vs pastiche

Whitman's sampler

noun
  • A diverse collection. 

pastiche

noun
  • A work of art, drama, literature, music, or architecture that imitates the work of a previous artist. 

  • A musical medley, typically quoting other works. 

  • An incongruous mixture; a hodgepodge. 

  • A postmodern playwriting technique that fuses a variety of styles, genres, and story lines to create a new form. 

verb
  • To create or compose in a mixture of styles. 

How often have the words Whitman's sampler and pastiche occurred in a corpus of books? (source: Google Ngram Viewer )