This is such an interesting question and whenever I see one of these phrases, I always wonder what the original colloquialisms and idioms are in the original languages, because I’m always really fascinated by different languages essentially saying the same things in such different ways. I’m an OL subber, so I translate from English to my native language, but I’ve also got a Bachelor’s Degree in English Language Teaching and Translation, so maybe I can give you a bit of insight on how it tends to go when it comes to translating these kinds of terms in any language in general.
Basically, the core of our translation classes was always “equivalence of meaning” and what that means is that sometimes for certain phrases (especially stuff like this), you might not have a single word match up to the original sentence, but the stuff that has to match up is the meaning, the connotation and the tone of the speaker. Certain idioms or even words can be essentially untranslatable and that’s when the work gets especially tricky and interesting, because you either have to do a deep dive into various dictionaries to look for that slim chance that something matches up to the OG or you just have to come up with a creative solution. Sometimes, there’s really nothing else to do other than keep the OG (whether you transcribe it or kind of give it a somewhat literal translation) and write a translator’s note and explain it. Whenever I think of this, I always think of my first translation lesson in college. In my language there’s a really specific word for the thing in which we boil coffee. It’s not a pot, it’s not a kettle, or any other English word. Similar, but absolutely none of those things. And whenever it pops up in texts that need to be translated, it’s really up to each translator to kind of just deal with it and be creative in transferring the meaning. The first project we got in that class was a very “simple” guide on how to make black coffee. You’d think that short of a text would be really easy to translate, but it actually took a lot of time for all of us and everyone’s text differed in terms of creative solutions.
I went a bit off track there, but some of these colloquialisms and idioms can really pose the same kind of challenge. I’m not sure what the original phrase was for the translation to be “knocked her up”, but for me that’s always had a bit of a negative connotation. If I heard someone “knocked someone up” I’d probably assume the couple or at least the speaker didn’t really see that in a positive light. I’d say it’s perfectly alright to use that phrase as a translation if the connotation of the original phrase was the same or if the context implied it, but if this isn’t the case and it’s meant to be a positive connotation in the original, although the words are correct, the translation wouldn’t be since the meaning isn’t equivalent.
As for certain slang terms being used in translation at all… Hmm, that’s a whole other other discussion, really. From a linguist’s point of view, I’m always relatively accepting of new terms and new creative uses of language, but it also really depends on the language. Some languages are quite open about accepting new terms and creatively using old ones, while some are not. English is one of those languages with which you can really play around with the language (like for example, adding a noun in front of another noun to modify that noun in order to create a new term to fit your purpose), so perhaps this is why these terms are kind of sneaking in there.
Anyway, I’m going to stop here, because I feel like this is turning out to be like one of my little monologues that I always do whenever I hang out with any of my classmates. I could honestly talk about language nuances for days if given the chance. Hahaha! Really interesting topic, though, and I’d love to hear more insight from other translators, especially those of you that speak Korean and have actually seen this phrase or phrases like it pop up in the English translations. I’d love to hear how you’d rate them in terms of accuracy when it comes to the original meaning in the original language.