operate vs ply

operate

verb
  • To put into, or to continue in, operation or activity; to work. 

  • To deal in stocks or any commodity with a view to speculative profits. 

  • To perform some manual act upon a human body in a methodical manner, and usually with instruments, with a view to restore soundness or health, as in amputation, lithotomy, etc. 

  • To act or produce effect on the mind; to exert moral power or influence. 

  • To perform a work or labour; to exert power or strength, physical or mechanical; to act. 

  • To produce, as an effect; to cause. 

  • To produce an appropriate physical effect; to issue in the result designed by nature; especially (medicine) to take appropriate effect on the human system. 

ply

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. 

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

  • A layer of material. 

  • A bent; a direction. 

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

  • A condition, a state. 

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