helper vs sustainer

helper

noun
  • A person who does cleaning and cooking in a family home, or in a market; domestic employee. 

  • That which helps; anything serving to assist. 

  • One who helps; an aide; assistant; auxiliary. 

  • A locomotive that assists a train, usually on steep gradients. 

sustainer

noun
  • A person or thing that sustains. 

  • A person who makes regular donations, especially to a public radio or television station. 

  • A rocket engine that remains with a spacecraft during its ascent after the separation of the booster engines. 

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