assignation vs double date

assignation

noun
  • An appointment for a meeting, generally of a romantic or sexual nature. 

  • The act of assigning or allotting; apportionment. 

  • A making over by transfer of title; assignment. 

double date

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

verb
  • To go on a double date. 

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