commutation vs disconnector

commutation

noun
  • The reversal of an electric current. 

  • The change to a lesser penalty or punishment by the State 

  • Substitution, as a means of discriminating between phonemes. 

  • The process or habit of journeying to and from work on a regular basis; commuting. 

  • Substitution of one thing for another; interchange. 

  • Specifically, the substitution of one kind of payment for another, especially a switch to monetary payment from obligations of labour. 

disconnector

noun
  • A switching device used to open an electric circuit when there is no current through it. They are used to isolate a part of an electrical system to allow the maintenance staff a safe access to it. 

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