co-mother-in-law vs relation

co-mother-in-law

noun
  • The mother of one's children-in-law; that is, the mother-in-law of one's children, or, the mother of one spouse in relation to the parents of the other spouse; either of two or more women whose children marry each other, such as the mother of a bride vis-à-vis the mother of the groom. 

relation

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

  • 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. 

  • The act of intercourse. 

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

  • The act of relating a story. 

  • 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 co-mother-in-law and relation occurred in a corpus of books? (source: Google Ngram Viewer )