sapper vs tanker

sapper

noun
  • An officer or private of the Royal Engineers. 

  • Historical term for a combat engineer that is still used in some armies, in other words an engineer or a soldier engaged in attacking, destroying, and circumventing or building fortifications, bridges, and roads; a military engineer active in a combat zone. 

tanker

noun
  • Member of a tank crew, or of an armoured unit. 

  • A tank ship, a vessel used to transport large quantities of liquid. 

  • A longboard. 

  • An aircraft built or modified to carry water and/or fire retardant for dropping on wildfires. 

  • A tank truck. 

  • A fuel tanker, petrol tanker, road tanker. 

  • An aircraft carrying a large supply of jet fuel or avgas for aerial refueling of other aircraft, plus equipment allowing the in-air transfer of fuel. 

  • A tank car. 

verb
  • To carry more fuel than necessary for a flight, in order to avoid having to refuel at a destination where fuel is more expensive or in short supply. 

  • To transport (oil, etc.) in a tanker. 

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