When I have watched EWTN, I have heard people speak of the Catholic Church as “Holy Mother Church”. What is the origin of that term?
The term I think came from the Book of Revelation. The Church is symbolically seen as the Bride of Lamb, or the Bride of Christ.
Like a Mother, the Church nurture the faithful spiritually by providing the means of salvation for the lay Catholics.
Describing the Church as a mother seems to come from the Bible, such as Galatians 4:26, 31 and Revelation 12:1-17, especially verse 17.
In the treatise On Re-Baptism by an anonymous writer, written about A.D. 255, these phrases appear: “our most holy mother the Church,” “our mother the Church” (paragraph 1), and “our most holy mother Church” (paragraph 6).
St. Cyril of Jerusalem, writing about A.D. 347, in his Catechetical Lecture 18, describes the Holy Catholic Church as “the mother of us all,” seemingly because, when we were baptized in the Catholic Church, we “were regenerated,” that is, born again (paragraph 26).