It’s sort of neat when fantasy/sci-fi manages to pull off coming up new curse words/expletives (though the only one I can think of that sounded good was in the Broken Earth Trilogy with the “evil Earth!” and “Earth burn it” kind of thing)
however, my ABSOLUTE favorite thing is the Adventure Time method where they just use already-existing words as swears. I think that’s hilarious like “Sodium! I stubbed my toe.” or “Milky Duds, this is bad.”
Can you imagine using Jeffrey as a curse word? I’m in love.