We are taught mostly British English but on the TV most of the programs in English come from the USA, with subtexts to broaden our vocabulary.
So there was this young Finnish girl as an Au Pair in Britain, in an upper class family near London. In the family there was two kids. Now, one evening the young rascals weren't behaving as their nanny wished, so to their mother's shock she called them "bastards". I don't know if there's any exact translation in the English language for the word used in the Finnish subtexts, but sheetling would be the closest I can figure. Sheethead, although being close, translates word by word. Anyway, the subtext translation is much milder than the original expression hinting the offspring being a result of unprotected swapping.