attic vs grey matter

attic

noun
  • A person's head or brain. 

  • The space, often unfinished and with sloped walls, directly below the roof in the uppermost part of a house or other building, generally used for storage or habitation. 

grey matter

noun
  • Brains; a person's ability to think. 

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

  • Literal brains as a general substance. 

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