In the days of the early Christian church, only Easter Sunday was celebrated as a holy day. By the fourth century, each day of the week preceding Easter were established as holy days including Good Friday.
To most Christians, Good Friday is really a misnomer in that it was a "bad" Friday—the crucifixion day of Jesus. Some believe the term "Good" evolved from "God" or God's Friday. Others believe "good" represents the good gift of salvation brought forth by the martyrdom. Regardless, it is a holy day throughout the Christian world.