leakproof vs waterfast

leakproof

adj

  • Resistant to leaks; hermetic, sound; as of a dry cell battery. 

verb

  • To make resistant to leakage. 

waterfast

adj

  • waterproof 

  • watertight 

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