We see an earlier form of semi-private confession as early as the 4th - 6th century in this quote of the Desert Fathers, the early monastics: If impure thoughts trouble you, do not hide them, but tell them at once to your spiritual father and condemn them. The more a person conceals his thoughts, the more they multiply and gain strength. But an evil thought, when revealed, is immediately destroyed. If you hide things, they have great power over you, but if you could only speak of them before God, in the presence of another, then they will often wither away, and lose their power.
So in Eastern Orthodoxy, we confess to God, kneeling before an icon of Christ, before the priest who serves as a witness. The Greek Orthodox absolution reads, "Let us pray to the Lord. O Lord and god of the salvation of Your servants, gracious, and merciful, and long-suffering, Who is grieved at our misdeeds, Who desires not the death of the sinner, but rather that he should be converted and live, have mercy now upon Your servant (handmaid) N.; grant him (her) true penitence, and the pardon and forgiveness of sins; remit to him (her) all transgressions, both voluntary and involuntary; reconcile and unite him (her) with Your Holy Church through Jesus Christ Our Lord, with Whom be power and glory ascribed unto You, now and ever, and to ages of ages. Amen.”