adoptive mother vs mamma

adoptive mother

noun
  • A woman who has adopted a child, as opposed to a biological mother. 

mamma

noun
  • The milk-secreting organ of female humans and other mammals which includes the mammary gland and the nipple or teat; a breast; an udder. 

  • An accessory cloud like a mammary in appearance, which can form on the underside of most cloud genera. 

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