The holy scriptures are older yet Christians care what is written in them.
"Jesus"
Jesus is the proper name of the God-man and signifies Saviour: a name given Him not accidentally, or by the judgement or will of man, but by the counsel and command of God. For the Angel announced to Mary His mother: Behold thou shalt conceive in thy womb, and shalt bring forth a son; and thou shalt call his name Jesus. He afterwards not only commanded Joseph, who was espoused to the Virgin, to call the child by that name, but also declared the reason why He should be so called. Joseph, son of David, said the Angel, fear not to take unto thee Mary thy wife, for that which is conceived in her is of the Holy Ghost. And she shall bring forth a son and thou shalt call his name Jesus. For he shall save his people from their sins.
In the Sacred Scriptures we meet with many who were called by this name. So, for example, was called the son of Nave, who succeeded Moses, and, by special privilege denied to Moses, conducted into the land of promise the people whom Moses had delivered from Egypt; and also the son of Josedech, the priest. But how much more appropriate it is to call by this name our Saviour, who gave light, liberty and salvation, not to one people only, but to all men, of all ages to men oppressed, not by famine, or Egyptian or Babylonian bondage, but sitting in the shadow of death and fettered by the galling chains of sin and of the devil who purchased for them a right to the inheritance of heaven and reconciled them to God the Father! In those men who were designated by the same name we see foreshadowed Christ the Lord, by whom the blessings just enumerated were poured out on the human race.
All other names which according to prophecy were to be given by divine appointment to the Son of God, are comprised in this one name Jesus; for while they partially signified the salvation which He was to bestow upon us, this name included the force and meaning of all human salvation.
"Christ"
To the name Jesus is added that of Christ, which signifies the anointed. This name is expressive of honour and office, and is not peculiar to one thing only, but common to many; for in the Old Law priests and kings, whom God, on account of the dignity of their office, commanded to he anointed, were called christs. For priests commend the people to God by unceasing prayer, offer sacrifice to Him, and turn away His wrath from mankind. Kings are entrusted with the government of the people; and to them principally belong the authority of the law, the protection of innocence and the punishment of guilt. As, therefore, both these functions seem to represent the majesty of God on earth, those who were appointed to the royal or sacerdotal office were anointed with oil. Furthermore, since Prophets, as the interpreters and ambassadors of the immortal God, have unfolded to us the secrets of heaven and by salutary precepts and the prediction of future events have exhorted to amendment of life, it was customary to anoint them also.
When Jesus Christ our Saviour came into the world, He assumed these three characters of Prophet, Priest and King, and was therefore called Christ, having been anointed for the discharge of these functions, not by mortal hand or with earthly ointment, but by the power of His heavenly Father and with a spiritual oil; for the plenitude of the Holy Spirit and a more copious effusion of all gifts than any other created being is capable of receiving were poured into His soul. This the Prophet clearly indicates when he addresses the Redeemer in these words: Thou hast loved justice, and hated iniquity: therefore God, thy God, hath anointed thee with the oil of gladness above thy fellows. The same is also more explicitly declared by the Prophet Isaias: The spirit of the Lord is upon me, because the Lord hath anointed me: he hath sent me to preach to the meek.
Jesus Christ, therefore, was the great Prophet and Teacher, from whom we have learned the will of God and by whom the world has been taught the knowledge of the heavenly Father. The name prophet belongs to Him preeminently, because all others who were dignified with that name were His disciples, sent principally to announce the coming of that Prophet who was to save all men.
Christ was also a Priest, not indeed of the same order as were the priests of the tribe of Levi in the Old Law, but of that of which the Prophet David sang: Thou art a priest for ever according to the order of Melchisedech. This subject the Apostle fully and accurately develops in his Epistle to the Hebrews.
Christ not only as God, but also as man and partaker of our nature, we acknowledge to be a King. Of Him the Angel testified: He shall reign in the house of Jacob for ever. And of his kingdom there shall be no end. This kingdom of Christ is spiritual and eternal, begun on earth but perfected in heaven. He discharges by His admirable Providence the duties of King towards His Church, governing and protecting her against the assaults and snares of her enemies, legislating for her and imparting to her not only holiness and righteousness, but also the power and strength to persevere. But although the good and the bad are found within the limits of this kingdom, and thus all men by right belong to it, yet those who in conformity with His commands lead unsullied and innocent lives, experience beyond all others the sovereign goodness and beneficence of our King. Although descended from the most illustrious race of kings, He obtained this kingdom not by hereditary or other human right, but because God bestowed on Him as man all the power, dignity and majesty of which human nature is capable. To Him, therefore, God delivered the government of the whole world, and to this His sovereignty, which has already commenced, all things shall be made fully and entirely subject on the day of judgement.
"His Only Son"
In these words, mysteries more exalted with regard to Jesus are proposed to the faithful as objects of their belief and contemplation; namely, that He is the Son of God, and true God, like the Father who begot Him from eternity. We also confess that He is the Second Person of the Blessed Trinity, equal in all things to the Father and the Holy Ghost; for in the Divine Persons nothing unequal or unlike should exist, or even be imagined to exist, since we acknowledge the essence, will and power of all to be one. This truth is both clearly revealed in many passages of Holy Scripture and sublimely announced in the testimony of St. John: In the beginning was the Word, and the Word was with God, and the Word was God.
But when we are told that Jesus is the Son of God, we are not to understand anything earthly or mortal in His birth; but are firmly to believe and piously to adore that birth by which, from all eternity, the Father begot the Son, a mystery which reason cannot fully conceive or comprehend, and at the contemplation of which, overwhelmed, as it were, with admiration, we should exclaim with the Prophet: Who shall declare his generation? On this point, then, we are to believe that the Son is of the same nature, of the same power and wisdom, with the Father, as we more fully profess in these words of the Nicene Creed: And in one Lord Jesus Christ, his Only-begotten Son, born of the Father before all ages, God of God, light of light, true God of true God, begotten, not made, consubstantial to the Father, by whom all things were made.
Among the different comparisons employed to elucidate the mode and manner of this eternal generation that which is borrowed from the production of thought in our mind seems to come nearest to its illustration, and hence St. John calls the Son the Word. For as our mind, in some sort understanding itself, forms an image of itself, which theologians express by the term word, so God, as far as we may compare human things to divine, understanding Himself, begets the eternal Word. It is better, however, to contemplate what faith proposes, and in the sincerity of our souls to believe and confess that Jesus Christ is true God and true Man, as God, begotten of the Father before all ages, as Man, born in time of Mary, His Virgin Mother.
While we thus acknowledge His twofold Nativity; we believe Him to be one Son, because His divine and human natures meet in one Person. As to His divine generation He has no brethren or coheirs, being the Only-begotten Son of the Father, while we mortals are the work of His hands. But if we consider His birth as man, He not only calls many by the name of brethren, but treats them as such, since He admits them to share with Him the glory of His paternal inheritance. They are those who by faith have received Christ the Lord, and who really, and by works of charity, show forth the faith which they profess in words. Hence the Apostle calls Christ, the first-born amongst many brethren.