high tide vs the flag is out

high tide

noun
  • Synonym of menstruation 

  • The natural tide at its highest level for a particular tidal cycle at a certain place. 

  • climax, culminating point or phase 

  • The time of day when the sea has risen to its highest level. 

the flag is out

How often have the words high tide and the flag is out occurred in a corpus of books? (source: Google Ngram Viewer )