conception vs grey matter

conception

noun
  • The power or faculty of apprehending of forming an idea in the mind; the power of recalling a past sensation or perception; the ability to form mental abstractions. 

  • An image, idea, or notion formed in the mind; a concept, plan or design. 

  • The act of conceiving. 

  • The fertilization of an ovum by a sperm to form a zygote. 

  • The state of being conceived; the beginning. 

  • The start of pregnancy. 

  • The formation of a conceptus or an implanted embryo. 

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