leave open vs safeguard

leave open

safeguard

noun
  • A safe-conduct or passport, especially in time of war. 

  • Something that serves as a guard or protection; a defense. 

  • One who, or that which, defends or protects; defence; protection. 

verb
  • To escort safely. 

  • To implement safeguarding. 

  • To protect, to keep safe. 

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