The doctrine of the communicatio idiomatum says that things which pertain to Christ’s human nature can be attributed to the Son of God, and things which pertain to the Logos can be attributed to Jesus, since these qualities adhere in a single person. Thus, it is not improper to say that Mary is the Mother of God, since she gave birth to Jesus, who is God, even though she did not produce his divine nature but only bore his human nature.
Origen mentions this and justifies it by citing certain biblical examples in his Commentary on Romans I, 6, 2:
… because of the inseparable unity of the Word and flesh, everything that is of the flesh is attributed to the Word also, since also the things which belong to the Word are foretold in the flesh. For we often find the designations “Jesus” and “Christ” and “Lord” referred to both natures. For example, “Our one Lord Jesus Christ through whom are all things” [1 Cor 8:6]; and again, “For if they would have known they would have never crucified the Lord of majesty” [1 Cor 2:8].
Of course, “Jesus” refers, strictly speaking, to the human nature of Christ which received that name (Luke 2:21). But this same Jesus, the human, is also called the “Lord … through whom are all things,” a designation proper to the divine nature. The blending of the attributes, one specifying one nature while another specifies the other, in such a smooth and unified manner, provides a basis for the notion of the communicatio idiomatum.