double date vs step out

double date

verb
  • To go on a double date. 

noun
  • A (romantic) date that two couples go on together. 

step out

verb
  • To date, to be in a romantic relationship. 

  • To exit a place on foot, often for a short time. 

  • To increase the length, but not the rapidity, of the step. 

How often have the words double date and step out occurred in a corpus of books? (source: Google Ngram Viewer )