duty vs tax

duty

noun
  • The state of being at work and responsible for or doing a particular task. 

  • That which one is morally or legally obligated to do. 

  • A tax placed on imports or exports; a tariff. 

  • The efficiency of an engine, especially a steam pumping engine, as measured by work done by a certain quantity of fuel; usually, the number of pounds of water lifted one foot by one bushel of coal (94 lbs. old standard), or by 1 cwt. (112 lbs., England, or 100 lbs., United States). 

tax

noun
  • A task exacted from one who is under control; a contribution or service, the rendering of which is imposed upon a subject. 

  • A burdensome demand. 

  • Money paid to the government other than for transaction-specific goods and services. 

verb
  • To impose and collect a tax from (a person or company). 

  • To impose and collect a tax on (something). 

  • To accuse. 

  • To make excessive demands on. 

  • To examine accounts in order to allow or disallow items. 

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