add-on vs contenement

add-on

noun
  • Something which can be appended to something else. 

  • A software extension or hardware peripheral that provides additional functions or customization for a core application or system. 

  • Additional chips that can be purchased at specific times in tournament play. 

contenement

noun
  • That which is held together with another thing. 

  • That which is connected with a tenement, or thing holden, as a certain quantity of land adjacent to a dwelling, and necessary to the reputable enjoyment of the dwelling. 

How often have the words add-on and contenement occurred in a corpus of books? (source: Google Ngram Viewer )