What is the difference between "a child is born" and "a son is given"?

What is the difference in Isaiah 9:6. between the expressions the “child born” and the “Son given”?

There is an important difference, I believe, and one which the exponents of what they term “the New Light,” as to the Eternal Sonship of our Lord, would do well to consider. Why is the “child” said to be “born,” but the “Son” not born, but “given”? We read in Isaiah 7:14 that God had been pleased to offer to king Ahaz a sign to confirm his doubting soul, that the line of David would not be superseded by the son of Tabeal, according to the Satanic design of Rezin and Pekah, which would have set aside the purpose of God regarding His future King, who must be of the seed of David according to the flesh. Ahaz had liberty of choice; he might ask for any sign in the depth, that is commensurate with the drying up of the Red Sea, or in the height commensurate with the standing still of the sun in answer to Joshua’s prayer. The king who was continually tempting God by his disobedience, refused this offer: He would not tempt the Lord, he said. Very well, then, the Lord will give a sign greater than any other known so far in the history of the world—the Virgin Birth of Him who was God: “Behold a virgin shall conceive, and bear a son, and shall call His name Immanuel” (v. 14). A great effort of unbelief has been made to show that the word,” ‘almãh,” translated “virgin,” should be rather rendered “young married woman.” Such an objection hardly shows unusual scholarship, so much as a lack of common sense; for the fact of a young married woman having a son would be no sign at all. In this verse, in the phrase “a virgin shall. . . bear a son,” the same verb is used as in chap. 9. 6, “a child is born.” Here the Son is viewed as the Son of Mary in the sense of Matthew 1:25: “She brought forth her first-born Son.” Why then is the “Son” said to be “given” in Isa. 9. 6? The reason is that there the One born is viewed as the One who had already been Son from all eternity. He could not become that by human birth. The child was born, but God gave His Eternal Son. W.H.