In a typical Life of Brian moment, I heared someone say ” Whats so good about it?” Which is a fair question, I mean its meant to be the day that Jesus Christ, our so called Lord and Saviour was murdered for daring to suggest that people don’t treat each other like crap. So with that in mind, maybe it should be called “Awful Friday” or “Really Pretty Shit Friday”.
Bearing that in mind, some sources actually suggest that it isn’t actually Good Friday at all, this is just a natural mutation of God’s Friday. Other sources claim that good is a greeting meaning holy, in the way that people say “goodtide” at Christmas. According to the Baltimore Catechism which was one of the most Catholic school texts in the US up until the 1960s, Good Friday is good because Christ “showed His great love for man, and purchased for him every blessing” which is certainly a nice thought.
But I think that it really is one of those mysteries that is lost to time.