fire-retardant vs flameproof

fire-retardant

adj

  • Hard to ignite; not flammable. 

noun

  • A substance that makes an object resistant to burning. 

flameproof

adj

  • Resistant to catching fire. 

verb

  • To make flameproof. 

How often have the words fire-retardant and flameproof occurred in a corpus of books? (source: Google Ngram Viewer )