ply vs sluice box

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. 

sluice box

noun
  • A box with riffles along the bottom, used to trap heavier gold particles as water washes them and the other material along the box. 

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