On my blog about British words and expressions adopted in America, Not One-Off-Britishisms, I’ve written briefly a couple of times about “bollocks,” originally meaning testicles and since used in all sorts of colorful ways. (The link is the more recent post, and it has a link to the previous one.) I recommend the comments on both, many of which are relate to how offensive the term has been, until fairly recently, in Britain.
I imagine that the move to acceptability occurred following the 1977 album Never Mind the Bollocks, Here’s the Sex Pistols. The record company was actually brought to court on obscenity charges; it won. Incidentally, it appears that the album led to the change in the more common spelling of the word, from “ballocks” to “bollocks.” Check out this chart from Google Books Ngram Viewer, showing the incidence of the two words in British books: