ply vs should

ply

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

  • To work at (something) diligently. 

  • To press upon; to urge persistently. 

  • 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. 

should

verb
  • Used to give advice or opinion that an action is, or would have been, beneficial or desirable. 

  • Will be likely to (become or do something); indicates a degree of possibility or probability that the stated thing will happen or be true in the future. 

  • Indicates that something is expected to have happened or to be the case now. 

  • Used to express a conditional outcome. 

  • With verbs such as 'see' or 'hear', usually in the second person, used to point out something remarkable in either a good or bad way. 

  • To make a statement of what ought to be true, as opposed to reality. 

  • Used to impart a tentative, conjectural or polite nuance. 

  • Used to express what the speaker would do in another person's situation, as a means of giving a suggestion or recommendation. 

  • Simple past tense of shall. 

  • In questions, asks what is correct, proper, desirable, etc. 

  • Used to issue an instruction (traditionally seen as carrying less force of authority than alternatives such as 'shall' or 'must'). 

  • Used to form a variant of the present subjunctive, expressing a state or action that is hypothetical, potential, mandated, etc. 

noun
  • Something that ought to be the case as opposed to already being the case. 

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