During the 1950’s and '60’s in the UK there was a more communal development of gay culture, though the word ‘gay’ was not used in those days.
Prior to this gay people were a lot more isolated and stayed in very closed groups, gay people found it very difficult to meet other strangers who were gay.
Why it all changed is a matter to books on social development, but it did.
Suffice to say that although there was a desire for gay people to seek each other out, it was still very difficult due to the repressive nature of UK society toward them.
Gay people would take precautions against being outed by using terms that would be familiar to the like minded, and if a mistaken attempt at contact was made there was a danger of being reported to the police.
Somehow a system was developed, which is I’d guess too organised a way to imagine how things operated, and this included a ‘gay’ vocabulary and a recognised way of making contacts.
During this time it became common practice for gay men to make contact with each other in Gentlemens Lavatories, this is what became called ‘cottaging’.
It was all very cloak and dagger, the risks of being caught involved public trial and humiliation, there could be serious social and employment consequencies, and many gay men were under cover, being married but leading double lives, which would then fall apart under the stress.
This would lead to police hiding in adjacent cubicles listening in to private conversations, or observing through spyholes, or acting as possible contacts, all in the attempt to repress gay people.
It was all very sordid, and you could argue that the police themselves were the most significant part of that.
I would expect that this is a very British thing, we were very prudish and sexually repressed as a whole, if you were above 30 in the UK at the time, and not married then it could draw suspicion upon you about your sexuality, unless you were considered a ‘confirmed batchelor’ of the love 'em and leave 'em type.