double date vs interval

double date

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

verb
  • To go on a double date. 

interval

noun
  • A period of time. 

  • A connected section of the real line which may be empty or have a length of zero. 

  • An intermission. 

  • half time, a scheduled intermission between the periods of play 

  • The difference (a ratio or logarithmic measure) in pitch between two notes, often referring to those two pitches themselves (otherwise known as a dyad). 

  • Either of the two breaks, at lunch and tea, between the three sessions of a day's play 

  • A distance in space. 

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