hit someone when they are down vs pour fuel on the fire

hit someone when they are down

verb

  • Synonym of kick someone when they are down (“make things worse for someone in a difficult position”) 

pour fuel on the fire

verb

  • Synonym of add fuel to the fire 

How often have the words hit someone when they are down and pour fuel on the fire occurred in a corpus of books? (source: Google Ngram Viewer )