ability vs grey matter

ability

noun
  • A unique power of the mind; a faculty. 

  • A skill or competence in doing; mental power; talent; aptitude. 

  • The quality or state of being able; capacity to do or of doing something; having the necessary power. 

  • Physical power. 

  • The legal wherewithal to act. 

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 ability and grey matter occurred in a corpus of books? (source: Google Ngram Viewer )