canal boat vs lighter

canal boat

lighter

noun
  • A person who lights things. 

  • A flat-bottomed boat for carrying heavy loads across short distances (especially for canals or for loading or unloading larger boats). 

  • A device used to light things, especially a reusable handheld device for creating fire to light cigarettes. 

verb
  • To transfer cargo or fuel from (a ship), lightening it to make its draft less or to make it easier to refloat. 

  • To transfer (cargo or passengers) to or from a ship by means of a lighter or other small vessel. 

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