If the Friday before Easter is the day on which Jesus Christ was crucified, one might well ask why we’d call the day “Good Friday.”
Jesus Christ was crucified on Good Friday, as told in the Bible. One theory estimates the actual date might have been April 3, 33, but trying to pinpoint an actual date is a subject of ongoing debate and doesn’t really matter beyond the attempt to satisfy some curiosity.
When we get bogged down over the date, we’re missing a much bigger point.
Christians believe that on Good Friday, Christ died on a cross to suffer the sins for all of us. On the third day, which became known as Easter Sunday, Christ rose from the dead through resurrection and was seen by several witnesses. It is through this penance that Christians are able to seek and achieve salvation through declaring Jesus Christ their Lord and personal Savior.
While Good Friday is a somber occasion, in which even the most contemporary churches resort to very old-school liturgical services to remind parishioners of the sacrifice, Easter Sunday is a vibrant celebration of the victory of Christ over death and, thereby, the hope for everlasting life for Christians themselves.
But at those aforementioned heavily-liturgical services held every Friday, where somberness is intentional, the  “good”  in Good Friday seems a mismatch.
Experts aren’t certain where good came from in that usage. Some sources, according to Wikipedia, insist that good refers to the holy aspect of the day, which suggests that it should or could also be known as Holy Friday. Others argue that good is a simple corruption of the word God, which seems rather unlikely to me, since it’s a religious day.
Some people, however, do refer to Good Friday as “Holy Friday,” “Great Friday,” or even “Black Friday.”
To me, the good has always referred to the fulfillment of prophecy that provided the gift of salvation. Even if the day itself isn’t treated as a reason to celebrate anything. The good referred to the end, not the means to that end.
Not to mention the grounding effect that the reminder of God’s sacrifice of His Son can have as we reflect on our own walk with Christ and our duty as Christians to love God with all our hearts and project the love that empowers us to have for ourselves to those around us.