FURTHER THOUGHTS
The OP said she got it as a result of something someone had posted.
Something that was posted that I overlooked in my collected theory posts and didn't get much traction was this:
@BollocksToBrexit
Is it to do with Christmas? 'Bos' has no 'well'. No well. Noel. Christmas?
This also slightly ties in with @coolwalking 's post at the end of the secon thread Wed 05-Dec-18 22:43:28
Exactly!! The joke is that some people know him as bos but you know him as "well". Boswell
If you don't know him as well then you don't have the answer and can't be told
CAN ANYONE STILL INTERESTED/OBSESSED HELP WITH THIS AS A FURTHER THOUGHT?:
I think the answer is somewhere in this area - something to do with "no well"/ "noel"/"know well" - but there needs to be a tie in with the end of the joke (about going up the steps/approaching the library) that we are currently missing
Something that creates a whole phrase like "no well before[?]" or "the first noel [?]" or "noel [?]" or "know well in front of [?] - where the [?] connects to his location before/in front of the library/post office.
Also OP posted this on the first thread:
killingtime9198 Tue 04-Dec-18 14:02:58
Reading all of this with amusement.
My friend and her husband didn't get given the answer on their wedding day - they both worked it out.
For those who still care - I put the 'four/for' suggestion to her and that's not it. She said 'it's not so much about the content of the joke', so it must be something in the way you tell it. That said, I asked her to tell me it over text and she did, so I don't think it can be something you PHYSICALLY do.
For context the joke is either:
'There once was a man called Boswell. For short they called him Bos, and he walked up the post office steps.'
or
'There was a man, whose name was boswell. And for short they called him bos. And he walked up the post office steps' ' [this was the revised written version provided by the OP's friend by text.
and the following should be noted:
killingtime9198 Mon 03-Dec-18 14:12:13
More - I asked if he was going to the post office to collect the letters missing from his name. She said no.
. . .
It doesn't matter that he walks up the steps - the joke still works if he just approaches the post office.
It doesn't matter that it's a post office, I asked if a library would also work, she said yes. I said:
'So this works: 'there one was a woman called Boswell. For short they called her Bos. And she walked up to the library'
She said yes