instability vs marbles

instability

noun
  • The quality of being unstable. 

  • A state that is not in equilibrium, or in which a small change has a large irreversible effect. 

marbles

noun
  • Sanity. 

  • Bits of rolled-up rubber shed by the tires of race cars that accumulate at the edges of the track, especially at the corners. 

  • Any of several children's games played with small balls (made of marble or more commonly glass). 

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