under the radar vs under the table

under the radar

prep
  • Without attracting notice; in an undetected or secretive manner. 

under the table

prep
  • Secretly; covertly; undisclosedly. 

  • Used other than figuratively or idiomatically: see under, table. 

  • In or into a state of stupification or boredom. 

  • In or into a state of drunkenness. 

  • Secret; covert; undisclosed. 

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