SOS vs indication

SOS

noun
  • A children's game in which players take turns to place S's and O's on a grid, collecting points by creating an "SOS" sequence. 

  • The conventional Morse code call made by a ship in distress. 

indication

noun
  • Any symptom or occurrence in a disease, which serves to direct to suitable remedies. 

  • That which serves to indicate or point out; mark; token; sign; symptom; evidence. 

  • Act of pointing out or indicating. 

  • Discovery made; information. 

  • An declared approximation of the price at which a traded security is likely to commence trading. 

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