Good Friday is a solemn day as far as the Christian faith is concerned, marking the anniversary of the crucifixion of Jesus Christ, who died on a Friday around the year 33 AD, according to historians.
There is little good to celebrate about the torture of any man, seemingly, but the name has persisted through time and is not a misnomer.
Good Friday, most importantly for Christians, marks the day that Jesus died for man's sins, which united the fledgling religion under a common martyr and idea. The results of Jesus' crucifixion, therefore, were very good.
Linguistic trivia is also at play here. The name may be derived from "God's Friday," the encyclopedia of the Catholic Church proposes, in the same way that Goodbye is a contraction of "God be with ye."
More substantiated is its link to Old English. Spoken in the British Isles from approximately 500 to 1100 AD, that language commonly employed the word "good" as a synonym for "holy," in the sense of something being true and pure. It is also why the Bible is sometimes called the Good Book. Orthodox Christians, in fact, call the day Great and Holy Friday.
Religious Christians commemorate Good Friday with a subdued service and hymns and are not permitted to hold Mass.