lifeboat vs supply vessel

lifeboat

noun
  • A boat especially designed for saving the lives of shipwrecked people or people in distress at sea (either launched from the shore with a crew, or else carried on board a larger ship). 

  • An emergency vehicle carried aboard a spaceship. 

verb
  • To rescue; to carry to safety 

supply vessel

noun
  • A ship used to transport supplies to offshore installations such as oil and gas platforms. 

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