Saracen vs sons of Ishmael

Saracen

noun
  • A type of six-wheeled armoured personnel carrier. 

  • A member of a nomadic people from the Sinai near the Roman province of Arabia in the early centuries CE, who were specifically distinct from Arabs. 

sons of Ishmael

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