grey matter vs headpiece

grey matter

noun
  • Literal brains as a general substance. 

  • A collection of cell bodies and (usually) dendritic connections, in contrast to white matter. 

  • Brains; a person's ability to think. 

headpiece

noun
  • The head; the brain. 

  • A headstall. 

  • A decorative page heading used at the start of volumes or chapters. 

  • A headset. 

  • The top piece or part of various things. 

  • Something covering the head. 

  • Protecting cover for the head; a helmet. 

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