comforter vs sustainer

comforter

noun
  • A person who comforts someone who is suffering. 

  • A pacifier. 

  • A padded cover for a bed, duvet, continental quilt. 

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 comforter and sustainer occurred in a corpus of books? (source: Google Ngram Viewer )