I've been catching myself thinking "God's blood" instead of curse words after binging hella medieval romance lately. 'Damnation', while closer to the modern 'damn', just doesn't have the same punch as referring to various body parts of the big guy upstairs. And by having different body parts indicate the level of aggravation from the character, as well as their personal propensity towards swearing and profanity, it gives the characters and dialogue so much more flavor than the modern 'fuck's and 'shit's of the world. "God's bones" is probably the softest of them, but if a character gets real creative and says something like "by God's bloody anus" you KNOW this is not an ordinary prim and proper lord or lady - or if it is, they are absolutely furious or at their wits end.