oiler vs wetback

oiler

noun
  • A Mexican. 

  • 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. 

  • An oil tanker. 

  • An oil well. 

wetback

noun
  • A Mexican or Central American who illegally enters the United States of America from its southern border. 

  • A person of the mestizo race; a mojado. 

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