oiler vs water tender

oiler

noun
  • An assistant in the engine room of a ship, senior only to a wiper, mainly responsible for keeping machinery lubricated. 

  • One who or that which oils. 

  • A small (typically thumb-sized) metal container of oil, often containing an integral brush. 

  • An oilskin coat. 

  • A Mexican. 

  • An oil tanker. 

  • An oil well. 

water tender

noun
  • A first-class petty officer in charge in a fireroom, who supplies the boilers with water, sees that fires are properly cleaned and stoked, etc. 

  • A specialized firefighting apparatus designed for transporting water from a water source, such as a lake or hydrant, to a fire scene. 

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