message vs red flag

message

noun
  • A communication, or what is communicated; any concept or information conveyed. 

  • An errand. 

  • See messages (“groceries, shopping”). 

  • An underlying theme or conclusion to be drawn from something. 

verb
  • To send (something) as a message; usually refers to electronic messaging. 

  • To send a message or messages; to be capable of sending messages. 

  • To send a message to; to transmit a message to, e.g. as text via a cell phone. 

red flag

noun
  • A cue, warning, or alert; a sign or signal that something is wrong. 

  • A signal that the race must be stopped immediately (and possibly restarted). 

  • red rag 

  • A common symbol, usually in the form of a banner, for leftist revolutionary ideologies, especially socialism. 

  • In the United Kingdom and some other countries, a flag formerly used by a railway guard to warn the driver not to start the train. 

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