Ok, I know that doesn't answer the question of why we call it Good Friday. Despite the poor translation, Good Friday is an appropriate title for today. Good Friday is a term which reminds us that the Christian view is different from that of the rest of the world. I am reminded of St. Paul words in 1 Cor. 1:18-25.
The message of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God. For it is written: "I will destroy the wisdom of the wise, and the learning of the learned I will set aside." Where is the wise one? Where is the scribe? Where is the debater of this age? Has not God made the wisdom of the world foolish? For since in the wisdom of God the world did not come to know God through wisdom, it was the will of God through the foolishness of the proclamation to save those who have faith. For Jews demand signs and Greeks look for wisdom, but we proclaim Christ crucified, a stumbling block to Jews and foolishness to Gentiles, but to those who are called, Jews and Greeks alike, Christ the power of God and the wisdom of God. For the foolishness of God is wiser than human wisdom, and the weakness of God is stronger than human strength.Those who cannot see what it good about Good Friday are missing the complete story. During the crucifixion, I am sure the apostles could not imagine that they day would be called Good Friday. I am sure they couldn't see anything good about it. They watched Our Lord suffer and die in such a horrific manner. But, just like today's Liturgy, the story didn't end on Good Friday. On Easter Sunday Jesus conquered death and rose from the grave. Unlike the apostles during the crucifixion, we know the rest of the story. Therefore, while we mourn because Jesus suffered to save us from our sins, we also rejoice as we look forward to Easter.
This day is known by several titles, Good Friday, Holy Friday, Mourning Friday in Germany, and Great Friday by the Orthodox and Eastern Rite Churches. Each of these titles focuses on a different part of the mystery.