co-mother vs friend

co-mother

noun
  • In polygamy, a wife of one's father who is not one's mother; that is, co-wife of one's mother. 

  • In polygamy, the relationship between one co-wife and another, in respect to their children. 

  • In a lesbian couple, the nonbirth mother (partner of the birth mother) of a child, especially one who takes an equal role in mothering the child. 

friend

noun
  • A person, typically someone other than a family member, spouse or lover, whose company one enjoys and towards whom one feels affection. 

  • A lover; a boyfriend or girlfriend. 

  • Used as a form of address when warning someone. 

  • A spring-loaded camming device. 

  • A person with whom one is vaguely or indirectly acquainted. 

  • A person who backs or supports something. 

  • Used to refer collectively to a group of associated individuals, especially those comprising a cast, company, or crew 

  • A function or class granted special access to the private and protected members of another class. 

  • An associate who provides assistance. 

  • An object or idea that can be used for good. 

verb
  • To add (a person) to a list of friends on a social networking site; to officially designate (someone) as a friend. 

How often have the words co-mother and friend occurred in a corpus of books? (source: Google Ngram Viewer )