This is not a question about slang, but about swearing and word creation.
I have a character who uses swear words, and this is part of his voice. I do not use real swear words. I want the sense of those words in the story. But not the words.
Other characters, in other parts of my world, simply use descriptive phrases effectively, no swear words. The two approaches to 'swearing' tells us where characters grew up, etc.
I've seen authors make up swear words that look like, and have an etymology similar to, real swear words - but are not actually swear words. (Like 'frak' on BSG.)
Here's what I have done instead, to incorporate swearing into the story: In my story, two different words for the concept of God/heavenly father/lord, are fake words derived from author-of-life, and from beautiful idol.
When I read these fake words, they make sense, and I think a reader who realizes the fake word is related to, for example, 'beautiful idol,' will 'get it.'
The problem is, when critique groups read my passages, they routinely get hung up on the fake words. They also don't understand why I am 'translating' the dialogue, but not the swear words, into regular English.
I don't understand this. Before I prune these words out altogether (because I'd prefer to keep them as character voice and religious tradition), I'd like to find out if there are guidelines.
My Question: What is the best way to introduce fake swear words so that they are assimilated easily by the reader? Is there a rule of thumb as to how many such words could be introduced per chapter?
I'm considering solutions like: the first two occurrences of the 'author' word to be firmly planted within a phrase we'd recognize. "By author above, you will not hurt my child!" or, "I swear by author-of-life that I did not raid that cookie jar!" And then, after a couple of instances where the swear word is inside a phrase we'd recognize, I can use the word for 'God' all on its own. (The short and long versions roughly equate to God and God-in-Heaven).
Is this the solution? I am not seeing current authors make up fake words like this, but I would like to. Another solution is to have a character explain to another character - 'Oh, that word loosely translates to 'God.' '
Edit - Happy to report that people reading recent drafts have no issue with the swear words. I'm down to three. The word for 'shit' is introduced after saying that something smells like sewage. The word for God is used within contextual sentences, like the example of 'Crom' given in comments. The word for 'hell' is close enough to words we would recognize that it parses. I took out the other swear words, though I think I still have a 'god-damn' in there, a single instance, with plans to use it in book 2.