grey matter vs upper storey

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. 

upper storey

noun
  • A person's brain. 

  • Used other than figuratively or idiomatically: see upper, storey. 

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