double date vs relation

double date

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

verb
  • To go on a double date. 

relation

noun
  • The act of intercourse. 

  • The manner in which two things may be associated. 

  • A set of ordered tuples. 

  • A set of ordered tuples retrievable by a relational database; a table. 

  • Specifically, a set of ordered pairs; a binary relation. 

  • The act of relating a story. 

  • A member of one's extended family; a relative. 

  • A statement of equality of two products of generators, used in the presentation of a group. 

  • A subobject of a product of objects. 

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