looming vs on the boil

looming

on the boil

prep
  • About to happen; imminent. 

  • Playing exceptionally well. 

  • Going smoothly; working well. 

  • continuing; active; in a state of activity or development. 

  • simmering strongly and about to boil. 

  • boiling. 

  • (Of a player taking a pass) running at full speed towards the opposition. 

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