Objection 1. It would seem that an unsuitable name was given to Christ. For the Gospel reality should correspond to the prophetic foretelling. But the prophets foretold another name for Christ: for it is written (Isaiah 7:14): "Behold a virgin shall conceive and bear a son, and His name shall be called Emmanuel"; and (Isaiah 8:3): "Call His name, Hasten to take away the spoils; Make haste to take away the prey"; and (Isaiah 9:6): "His name shall be called Wonderful, Counselor God the Mighty, the Father of the world to come, the Prince of Peace"; and (Zechariah 6:12): "Behold a Man, the Orient is His name." Thus it was unsuitable that His name should be called Jesus.
Objection 2. Further, it is written (Isaiah 62:2): "Thou shalt be called by a new name, which the mouth of the Lord hath named [Vulgate: 'shall name']." But the name Jesus is not a new name, but was given to several in the Old Testament: as may be seen in the genealogy of Christ (Luke 3:29), "Therefore it seems that it was unfitting for His name to be called Jesus."
Objection 3. Further, the name Jesus signifies "salvation"; as is clear from Matthew 1:21: "She shall bring forth a son, and thou shalt call His name Jesus. For He shall save His people from their sins." But salvation through Christ was accomplished not only in the circumcision, but also in uncircumcision, as is declared by the Apostle (Romans 4:11-12). Therefore this name was not suitably given to Christ at His circumcision.
On the contrary is the authority of Scripture, in which it is written (Luke 2:21): "After eight days were accomplished, that the child should be circumcised, His name was called Jesus."
I answer that, A name should answer to the nature of a thing. This is clear in the names of genera and species, as stated Metaph. iv: "Since a name is but an expression of the definition" which designates a thing's proper nature.
Now, the names of individual men are always taken from some property of the men to whom they are given. Either in regard to time; thus men are named after the Saints on whose feasts they are born: or in respect of some blood relation; thus a son is named after his father or some other relation; and thus the kinsfolk of John the Baptist wished to call him "by his father's name Zachary," not by the name John, because "there" was "none of" his "kindred that" was "called by this name," as related Luke 1:59-61. Or, again, from some occurrence; thus Joseph "called the name of" the "first-born Manasses, saying: God hath made me to forget all my labors" (Genesis 41:51). Or, again, from some quality of the person who receives the name; thus it is written (Genesis 25:25) that "he that came forth first was red and hairy like a skin; and his name was called Esau," which is interpreted "red."
But names given to men by God always signify some gratuitous gift bestowed on them by Him; thus it was said to Abraham (Genesis 17:5): "Thou shalt be called Abraham; because I have made thee a father of many nations": and it was said to Peter (Matthew 16:18): "Thou art Peter, and upon this rock I will build My Church." Since, therefore, this prerogative of grace was bestowed on the Man Christ that through Him all men might be saved, therefore He was becomingly named Jesus, i.e. Saviour: the angel having foretold this name not only to His Mother, but also to Joseph, who was to be his foster-father.
Reply to Objection 1. All these names in some way mean the same as Jesus, which means "salvation." For the name "Emmanuel, which being interpreted is 'God with us,'" designates the cause of salvation, which is the union of the Divine and human natures in the Person of the Son of God, the result of which union was that "God is with us."
When it was said, "Call his name, Hasten to take away," etc., these words indicate from what He saved us, viz. from the devil, whose spoils He took away, according to Colossians 2:15: "Despoiling the principalities and powers, He hath exposed them confidently."
When it was said, "His name shall be called Wonderful," etc., the way and term of our salvation are pointed out: inasmuch as "by the wonderful counsel and might of the Godhead we are brought to the inheritance of the life to come," in which the children of God will enjoy "perfect peace" under "God their Prince."
When it was said, "Behold a Man, the Orient is His name," reference is made to the same, as in the first, viz. to the mystery of the Incarnation, by reason of which "to the righteous a light is risen up in darkness" (Psalm 111:4).
Reply to Objection 2. The name Jesus could be suitable for some other reason to those who lived before Christ--for instance, because they were saviours in a particular and temporal sense. But in the sense of spiritual and universal salvation, this name is proper to Christ, and thus it is called a "new" name.
Reply to Objection 3. As is related Genesis 17, Abraham received from God and at the same time both his name and the commandment of circumcision. For this reason it was customary among the Jews to name children on the very day of circumcision, as though before being circumcised they had not as yet perfect existence: just as now also children receive their names in Baptism. Wherefore on Proverbs 4:3, "I was my father's son, tender, and as an only son in the sight of my mother," the gloss says: "Why does Solomon call himself an only son in the sight of his mother, when Scripture testifies that he had an elder brother of the same mother, unless it be that the latter died unnamed soon after birth?" Therefore it was that Christ received His name at the time of His circumcision.
Source: Summa Theologica (New Advent)