imperial system vs thou

imperial system

noun
  • A system of measurement in use in the United Kingdom and other Commonwealth countries, now mostly superseded by the metric system; similar to the system currently used in the United States; consisting of units such as the inch, the mile and the pound (of weight). 

thou

noun
  • A unit of length equal to one-thousandth of an inch (25.4 µm). 

  • A thousand, especially a thousand of some currency (dollars, pounds sterling, etc.). 

verb
  • To use the word thou. 

  • To address (a person) using the pronoun thou, especially as an expression of contempt or familiarity. 

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