These are also not personal terms of reference for the three persons of the Trinity, but references to their functions. Imagine referring to your parents not as 'Dad and Mom' or even as George and Phyllis, but as 'Businessman and Housewife.'
Or if my wife referred to me as "consultant." Or worse.
Pope Benedict made a similar point in Jesus of Nazareth concerning God the Father and Christ's Sonship. He mentions the use of maternal language in the Old Testament, particularly the word rahamim or womb, which the Holy Father explains "is the most concrete epression for the intimate interrelatedness of two lives" (139). However, he continues on to explain that Israel was distinct in that it, unlike its neighbors, had a Father, God, rather than a mother deity:
By contrast, the image of the Father was and is apt for expressing the otherness of Creator and creature and the sovereignty of his creative act. Only by excluding the mother deities could the Old Testament bring its image of God, the pure transcendence of God, to maturity.
He continues on the scriptural bases for calling God the Father:
But even if we cannot provide any absolutely compelling arguments, the prayer language of the entire Bible remains normative for us, in which, as we have seen, while there are some fine images of maternal love, "mother" is not used as a title or a form of address for God. We make our petitions in the way Jesus, with Holy Scripture in the background, taught us to pray, and not as we happen to think or want. Only thus do we pray properly.
By the way, if you have not yet read Jesus of Nazareth you owe it to yourself to get your hands on a copy. Like most (if not all) of the Holy Father's books, it's an excellent read.