ply vs stratum

ply

noun
  • A layer of material. 

  • In two-player sequential games, a "half-turn" or a move made by one of the players. 

  • A bent; a direction. 

  • A strand that, twisted together with other strands, makes up rope or yarn. 

  • A condition, a state. 

verb
  • To work at (something) diligently. 

  • To press upon; to urge persistently. 

  • To persist in offering something to, especially for the purpose of inducement or persuasion. 

  • To travel over (a route) regularly. 

  • To bend, to flex; to be bent by something, to give way or yield (to a force, etc.). 

  • To wield or use (a tool, a weapon, etc.) steadily or vigorously. 

stratum

noun
  • One of several parallel horizontal layers of material arranged one on top of another. 

  • A layer of sedimentary rock having approximately the same composition throughout. 

  • Any of the regions of the atmosphere, such as the stratosphere, that occur as layers. 

  • A class of society composed of people with similar social, cultural, or economic status. 

  • A layer of vegetation, usually of similar height. 

  • The level of accuracy of a computer's clock, relative to others on the network. 

  • A layer of tissue. 

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