@goatsarah as somebody who grew up christian in a non-English speaking country, the name “Good Friday” also perplexes me.
We call it (a literal translation of) Holy Friday, and it's definitely set aside with specific rites and observances, but not celebrated as a joyous occasion, it's the exact opposite.
And I can get that the sound theological reasons may also apply to the name, but really, the good bit of the whole cleansing humanity from the original sin and stuff is the result, not the process, isn't it?