The Rice University Neologisms Database

The mother of a child in an unmarried man and woman couple. Apparent Meaning: The mother of a young child in an unmarried couple. It seems to refer specifically to a mother of an illegitimate infant or toddler rather than the progeny of a married couple. The noun root BABY refers to a very young child or infant. The noun root MAMMA is a slang term that means mother. The root BABY seems to take on a possessive form (baby’s), suggesting that the MAMMA in the term is that of the BABY, thereby establishing the relationship of a woman to a man, both of whom are parents of a common child. Possible Reason Used: The term seems to be a shortening of the phrase “baby’s mother” to a word that can be said much more easily and quickly. It also describes the relation of a woman to a man in an unmarried couple by simply suggesting that the woman is the mother of the couple’s baby. The term is used when a couple is not married, and the term “wife” cannot be appropriately applied. Also, the slang term provides a more specific description of a girlfriend; namely, a girlfriend who has had a child prior to marriage during a relationship. Thus, the term is often used in context of problematic relationships that are the topic of daytime talk shows and rap music.