capitation vs duty

capitation

noun
  • A poll tax. 

  • Performing a headcount; the counting of people. 

  • A system of remuneration for providers of health care, in which providers enroll patients as permanent clients and receive a fixed periodic payment for each enrollee. 

  • A donation made to an educational institution to obtain admission. 

duty

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

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

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

  • 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). 

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