The term Good Friday comes from the sense 'pious, holy' of the word good.[12] Less common examples of expressions based on this obsolete sense of good include 'the good book" for the Bible, 'good tide' for Christmas or Shrovetide, and Good Wednesday for the Wednesday in Holy Week.[13]
@aetios child me always thought it was weird that it was called good friday, turns out it's just an old meaning of the word good that died out