hexad vs octet

hexad

noun
  • A group of six. 

  • An element or radical with the combining power of six units, i.e. six atoms of hydrogen. 

octet

noun
  • A group or set of eight of something. 

  • A composition for such a group of musicians. 

  • A group of eight musicians performing together. 

  • A byte of eight bits. Abbreviation: o 

  • A group of three bits, representing any of eight possible values. 

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