haulage vs towboat

haulage

noun
  • The charge levied for hauling or pulling a ship or boat. 

  • The act of hauling. 

  • The business of transporting goods. 

towboat

noun
  • A steamer used for towing other vessels; a tug. 

  • A tugboat. 

  • A squat powerful boat designed to push barges. 

  • A vessel constructed for being towed, such as a canal boat. 

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