gush vs knock dead

gush

verb
  • To make an excessive display of enthusiasm, praise, or sentiment. 

  • To send (something) flowing forth suddenly in great volume. 

  • To ejaculate during orgasm. 

  • To flow forth suddenly, in great volume. 

noun
  • A sudden rapid outflow. 

knock dead

verb
  • To amaze or greatly impress (someone) by delivering an outstanding performance. 

How often have the words gush and knock dead occurred in a corpus of books? (source: Google Ngram Viewer )