bombproof vs mailed

bombproof

adj
  • Sufficiently strong to resist the effects of a blast from a bomb. 

verb
  • To make resistant to bomb blasts. 

noun
  • An air-raid shelter, a structure designed to give protection against air raids and bombs. 

mailed

adj
  • Resembling the scales of armor. 

  • Armoured in, protected by, or made of mail. 

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