I’ve never seen it used in the US. Here, BJ has always meant one of two things: oral sex or a truck driver who has a chimpanzee partner.
(Okay, that is a bit of an exaggeration.)
From the 1930’s:
IN, Never Give a Sucker an Even Break, a woman is looking at a billboard for WC Fields’ new movie, The Bank Dick. WC Fields comes up beside her and asks “Have you seen my Bank Dick?” She slaps him.
In some Marx Brothers movie, they are at a fancy party and some high society stuck up lady is insulted by Groucho. She says “Well, I never…!” (common phrase of the time)
Groucho replies, “There’s your problem! Maybe you should once in a while!”
(Fun story - I told that line to my nephews way back when, and my step-sister tells them not to use that line. Apparently their grandmother and her friends were still in habit of using that expression.)
For the OP - if anything, it’s because the degree of prurience has gotten less. TV couples in 50’s sitcoms slept in double beds. You never saw toilets in TV shows - it was 1970 when All In The Family made a running joke of Archie’s use of the toilet including flushing sounds. What could be shown in a theatre movie has gotten more and more lax over the decades. Along with media, general knowledge has become more “public”. (Think of what Bill Clinton did for general knowledge about oral sex.) Language is the same way. What was previously unsaid is now front page news. The innuendos have to be more common and explicit to keep up; and there is more in people’s minds to relate it to.
The double entendre has had a long career in English- there are plenty in Shakespeare, after all, plenty of folksongs where sexual meanings survived despite Victorian and Edwardian collectors’ bowdlerisations, and plenty of music-hall songs from well over a century ago that seem no more than mildly comic on the surface, but in the hands of a performer like Marie Lloyd or Harry Champion could be interpreted in quite another way. And there’s the British panto tradition - and George Formby with his little stick of Blackpool rock.
This brings to mind the Animaniacs, based on the Marx Brothers. Marketed as a kid’s show (as in, not like South Park or Family Guy, etc.) it didn’t shy away from the sexual innuendo (such as “pianist” jokes, and one about fingering Prince.)
I saw an interview with the British guy who played sax on Lou Reed’s Walk on the Wild Side. His attitude was “this a cool song, shame I will never hear it as there is no way they will play a song on British radio containing the line ‘even when she was giving head’”
Much to his amazement it was on BBC all the time. It turns the guardians of British morals at the Beeb had no idea what the term ‘giving head’ meant (this was in 1972).
Nitpick: What you’re talking about is a certain aspect of the English language becoming less gendered, not less sexualized.
Language use can be heavily sexualized, in the sense of including a lot of sexual innuendo and interpreting statements in a “dirty” way, even if it employs gender-neutral terms for occupations.
Another thought on this…
Double entendre in older media, such as music hall, is not necessarily proof that sexual taboos on language haven’t changed.
‘Back in the day’ when someone like a music hall comedian used a double entendre it literally had double meaning. He (and it was almost always a he) did not expect most of his audience to get the sexual connection. He knew there would be a portion of the male, adult, audience who would understand “nudge, nudge, wink, wink”, but the rest it was assumed would have no inkling.
When a modern TV show uses a double entendre it is assumed that most of the adult audience (and a good portion of the child audience) will get the joke.
Because sex sells.