commutation vs trek

commutation

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

  • 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. 

  • 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. 

trek

noun
  • A slow or difficult journey. 

  • A journey by ox wagon. 

  • The Boer migration of 1835-1837. 

  • A long walk. 

verb
  • To travel by ox wagon. 

  • To travel by walking. 

  • To journey on foot, especially to hike through mountainous areas. 

  • To make a slow or arduous journey. 

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