What are the rules of Isaiah's cussing?

I was raised Christian (but probably a different Christian) and I remember not being allowed to say "oh my god" because that was the only thing I would say as a kid. By the time I was of cussing age I was not religious. But I'd imagine you can't say "damn" because it's directly something referencing God, but why can't he say like "shit"? Truly just out of curiosity and I like learning the lore of Christianity.

Like for instance I used to go to a Lutheran church, and then in public school they taught me who Martin Luther is, and I was like yooo that's sick as hell, my mom picked the right branch of Christianity LOL.