acknowledge vs should

acknowledge

verb
  • To admit the knowledge of; to recognize as a fact or truth; to declare one's belief in 

  • To own as genuine or valid; to assent to (a legal instrument) to give it validity; to avow or admit in legal form. 

  • To own or recognize in a particular quality, character or relationship; to admit the claims or authority of; to give recognition to. 

  • To be grateful of (e.g. a benefit or a favour) 

  • To report (the receipt of a message to its sender). 

should

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

  • 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. 

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

  • 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 acknowledge and should occurred in a corpus of books? (source: Google Ngram Viewer )