allow vs constrain

allow

verb
  • To acknowledge; to accept as true; to concede; to accede to an opinion. 

  • To not bar or obstruct. 

  • To render physically possible. 

  • To grant, give, admit, accord, afford, or yield; to let one have. 

  • To grant license to; to permit; to consent to. 

  • To grant (something) as a deduction or an addition; especially to abate or deduct. 

  • To take into account by making an allowance. 

  • To decide (a request) in favour of the party who raised it; to grant victory to a party regarding (a request). 

constrain

verb
  • To force physically, by strong persuasion or pressuring; to compel; to oblige. 

  • To keep within close bounds; to confine. 

  • To reduce a result in response to limited resources. 

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