Is confession a late invention of Catholicism, or was it used from the earliest times? Let's see what the earliest writers say.
"Confess your sins in church, and do not go up to your prayer with an evil conscience. This is the way of life" (4:14 [as early as A.D. 70]).
"On the Lord's Day gather together, break bread, and give thanks, after confessing your transgressions so that your sacrifice may be pure" (14:1).
"[The gnostic disciples of Marcus] have deluded many women. . . . Their consciences have been branded as with a hot iron. Some of these women make a public confession, but others are ashamed to do this, and in silence, as if withdrawing from themselves the hope of the life of God, they either apostatize entirely or hesitate between the two courses" (Against Heresies 1:22 [A.D. 180]).
"[Regarding confession, some] flee from this work as being an exposure of themselves, or they put it off from day to day. I presume they are more mindful of modesty than of salvation, like those who contract a disease in the more shameful parts of the body and shun making themselves known to the physicians; and thus they perish along with their own bashfulness. Why do you flee from the partners of your misfortunes as you would from those who deride? The body is not able to take pleasure in the trouble of one of its members. It must necessarily grieve as a whole and join in laboring for a remedy" (On Repentance 10:1 [A.D. 203]).
"With one and two individuals, there is the Church; and the Church indeed is Christ. Therefore, when you cast yourself at the knees of the brethren, you are dealing with Christ, you are entreating Christ" (On Repentance 10:6).
"The Apostle likewise bears witness and says: . . . Whoever eats the bread or drinks the cup of the Lord unworthily will be guilty of the body and blood of the Lord. But [the impenitent] spurn and despise all these warnings; before their sins are expiated, before they have made a confession of their crime, before their conscience has been purged in the ceremony and at the hand of the priest . . . they do violence to his body and blood, and with their hands and mouth they sin against the Lord more than when they denied him" (The Lapsed 15:1-3 [A.D. 251]).
"Of how much greater faith and salutary fear are they who . . . confess their sins to the priests of God in a straightforward manner and in sorrow, making an open declaration of conscience. God cannot be mocked or outwitted, nor can he be deceived by any clever cunning. Indeed, he but sins the more if, thinking that God is like man, he believes that he can escape the punishment of his crime by not openly admitting his crime. . . . I beseech you, brethren, let everyone who has sinned confess his sin while he is still in this world, while his confession is still admissible, while the satisfaction and remission made through the priests are still pleasing before the Lord" (The Lapsed 28).
"It is necessary to confess our sins to those to whom the dispensation of God's mysteries is entrusted. Those doing penance of old are found to have done it before the saints. It is written in the Gospel that they confessed their sins to John the Baptist [Matt. 3:6], but in Acts [19:18] they confessed to the apostles." (Rules Briefly Treated 288 [A.D. 370]).
"Priests have received a power which God has given neither to angels nor to archangels. It was said to them: 'Whatsoever you shall bind on earth shall be bound in heaven; and whatsoever you shall loose, shall be loosed.' Temporal rulers have indeed the power of binding; but they can only bind the body. Priests, in contrast, can bind with a bond which pertains to the soul itself and transcends the very heavens. Did [God] not give them all the powers of heaven? 'Whose sins you shall forgive,' he says, 'they are forgiven them; whose sins you shall retain, they are retained.' What greater power is there than this? The Father has given all judgment to the Son. And now I see the Son placing all this power in the hands of men [Matt. 10:40; Luke 10:16; John 20:20-23; 2 Cor. 5:18-20]. They are raised to this dignity as if they were already gathered up to heaven." (On the Priesthood 3:5 [A.D. 386]).
"For those to whom [the right of binding and loosing] has been given, it is plain that either both are allowed, or it is clear that neither is allowed. Both are allowed to the Church, neither is allowed to heresy. For this right has been granted to priests only" (On Penance 1:1 [A.D. 387]).