bombshell vs fission bomb

bombshell

noun
  • A bomb or artillery shell designed to explode on impact. 

  • Something that is very surprising, shocking, amazing or sensational. 

  • Someone who is very attractive; a sex symbol. 

fission bomb

noun
  • An atomic bomb that uses nuclear fission as a source of energy 

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