capitulum vs read/write head

capitulum

noun
  • The head-like mouthpart apparatus of a tick, including the palpi, mandibles, and hypostome. 

  • A small protuberance on a bone which articulates into another bone to form a ball-and-socket joint. 

  • A densely clustered inflorescence composed of a large number of individual florets arising from a platform-like base. 

read/write head

noun
  • A combination read head and write head 

How often have the words capitulum and read/write head occurred in a corpus of books? (source: Google Ngram Viewer )