Whenever an author goes to create a world, soon or late they have to deal with the issue of swearing. Even if the decision is “not used in this language” it has to be dealt with.
One of the common options, especially in fantasy, is to invent gods to swear by, but this can sometimes come off as contrived. I therefore offer this small compilation of swearing patterns to assist those starting out.
A lot of swearing is some corruption of an expression of respect, when you think about it, the original form having been someone calling on their deity to witness their sincerity or truthfulness or, alternatively, the severity of the situation–possibly in hopes that, having noticed, the deity in question will fork over some assistance. This, of course, quickly devolves from deliberate calling upon to simple expression of exasperation, anger or other strong emotion. So the first question is: how for down this progression is the swearing in question?
If it’s still early days, some reliable formulae are “by deity-name!”, “by deity-name’s identifying-object!” or “deity-name significant-activity!”
A bit further on, you can start loosening the association with the actual deity. For example, if you take a body part associated with the significant activity, you can use “deity-name’s descriptive-adjective body-part!”. If the identifying object seems like a better bet, “deity-name’s descriptive-adjective identifying-object!” is also pretty standard. The degree of respect or facetiousness in the descriptive adjective should be matched to the manner of the character doing the swearing.
Eventually this can progress into the downright silly, at which point it may well start expanding also. For example: “deity-name on/in/with a strange-descriptive-adjective totally-unassociated-object”.
Now, if you decide you want to avoid deities entirely, you can always use animals instead. Some common variations on that are “domesticated-animal undesirable-byproduct!” or “domesticated-animal troublesome-behavior!”.
If you’re far enough along the aforementioned progression, you can even combine this with the deity version, for something like “deity-name troublesome-behavior!”.
One thing to remember in all this: don’t get too carried away with sniggering and go overboard. Otherwise you’ll wind up like Steve White, who is clearly a little too personally amused by the literal translation of some earthier Russian figures of speech.