The Fathers of the Church have referred to the Catholic Church as "Mother Church" from as early as the second century AD. This page lists quotes some of the best known Fathers on this topic.
When the loving and benevolent Father had rained down the Word, that Word then became the spiritual nourishment of those who had good sense. [42, 1] O mystic wonder! The Father of all is indeed one and the same everywhere; and one only is the Virgin Mother. I love to call her the Church. This Mother alone was without milk, because she alone did not become a wife. She is at once both Virgin and Mother: as a Virgin, undefiled; as a Mother, full of love.
Thus too the Church bathed in the light of the Lord projects its rays over the whole world, yet there is one light which is diffused everywhere, and the unity of the body is not separated. She extends her branches over the whole earth in fruitful abundance; she extends her richly flowing streams far and wide; yet her head is one, and her source is one, and she is the one mother copious in the results of her fruitfulness. By her womb we are born; by her milk we are nourished; by her spirit we are animated.
But since the word Ecclesia is applied to different things (as also it is written of the multitude in the theatre of the Ephesians, And when he had thus spoken, he dismissed the Assembly ), and since one might properly and truly say that there is a Church of evil doers, I mean the meetings of the heretics, the Marcionists and Manichees, and the rest, for this cause the Faith has securely delivered to thee now the Article, "And in one Holy Catholic Church;" that thou mayest avoid their wretched meetings, and ever abide with the Holy Church Catholic in which thou wast regenerated. And if ever thou art sojourning in cities, inquire not simply where the Lord's House is (for the other sects of the profane also attempt to call their own dens houses of the Lord), nor merely where the Church is, but where is the Catholic Church. For this is the peculiar name of this Holy Church, the mother of us all, which is the spouse of our Lord Jesus Christ, the Only-begotten Son of God (for it is written, As Christ also loved the Church and gave Himself for it , and all the rest,) and is a figure and copy of Jerusalem which is above, which is free, and the mother of us all ; which before was barren, but now has many children.
Unflaggingly, let us love the Lord our God and let us love his Church. Let us love Him as the Lord and the Church as his handmaid.
No one can offend the one and still be pleasing to the other. What does it avail you if you do not directly offend the Father but do offend the mother?