sestet vs sixsome

sestet

noun
  • A piece of music composed for six voices or six instruments; a sextet or sestuor. 

  • The last six lines of a sonnet, forming two stanzas of three lines each. 

sixsome

noun
  • A group of six persons or things. 

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